AP-4 complex subunit mu-1 isoform X3 [Homo sapiens]
Protein Classification
AP-4 complex subunit mu( domain architecture ID 13000792)
AP-4 complex subunit mu is the subunit of novel type of clathrin- or non-clathrin-associated protein coat involved in targeting proteins from the trans-Golgi network (TGN) to the endosomal-lysosomal system
List of domain hits
| Name | Accession | Description | Interval | E-value | |||||
| AP_MHD_Cterm super family | cl10970 | C-terminal domain of adaptor protein (AP) complexes medium mu subunits and its homologs (MHD); ... |
182-419 | 3.01e-102 | |||||
C-terminal domain of adaptor protein (AP) complexes medium mu subunits and its homologs (MHD); This family corresponds to the C-terminal domain of heterotetrameric AP complexes medium mu subunits and its homologs existing in monomeric stonins, delta-subunit of the heteroheptameric coat protein I (delta-COPI), a protein encoded by a pro-death gene referred as MuD (also known as MUDENG, mu-2 related death-inducing gene), an endocytic adaptor syp1, the mammalian FCH domain only proteins (FCHo1/2), SH3-containing GRB2-like protein 3-interacting protein 1 (SGIP1), and related proteins. AP complexes participate in the formation of intracellular coated transport vesicles and select cargo molecules for incorporation into the coated vesicles in the late secretory and endocytic pathways. Stonins have been characterized as clathrin-dependent AP-2 mu chain related factors and may act as cargo-specific sorting adaptors in endocytosis. Coat protein complex I (COPI)-coated vesicles function in the early secretory pathway. They mediate the retrograde transport from the Golgi to the ER, and intra-Golgi transport. MuD is distantly related to the C-terminal domain of mu2 subunit of AP-2. It is able to induce cell death by itself and plays an important role in cell death in various tissues. Syp1 represents a novel type of endocytic adaptor protein that participates in endocytosis, promotes vesicle tabulation, and contributes to cell polarity and stress responses. It shares the same domain architecture with its two ubiquitously expressed mammalian counterparts, FCHo1/2, which represent key initial proteins ultimately controlling cellular nutrient uptake, receptor regulation, and synaptic vesicle retrieval. They bind specifically to the plasma membrane and recruit the scaffold proteins eps15 and intersectin, which subsequently engage the adaptor complex AP2 and clathrin, leading to coated vesicle formation. Another mammalian neuronal-specific protein SGIP1 does have a C-terminal MHD and has been classified into this family as well. It is an endophilin-interacting protein that plays an obligatory role in the regulation of energy homeostasis. It is also involved in clathrin-mediated endocytosis by interacting with phospholipids and eps15. The actual alignment was detected with superfamily member cd09253: Pssm-ID: 472082 Cd Length: 271 Bit Score: 304.49 E-value: 3.01e-102
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| AP4_Mu_N | cd14838 | AP-4 complex subunit mu N-terminal domain; AP-4 complex mu subunit is part of the ... |
3-148 | 4.66e-72 | |||||
AP-4 complex subunit mu N-terminal domain; AP-4 complex mu subunit is part of the heterotetrameric adaptor protein (AP)-1 complex which consists of one large epsilon-, one beta-, one mu-, and one sigma-subunit. AP complexes link the cytosolic domains of the cargo proteins to the protein coat that induces vesicle budding in the donor compartment during vesicle transport. AP-4 does not bind the coat protein clathrin, it is associated with nonclathrin coats. Its phospholipid binding partner is unknown and it is localized in the trans-Golgi network (TGN). The mu subunit is comprised of an N-terminal longin domain followed by a C-terminal domain which is involved in the binding of the Y-X-X-Phi sorting signal. : Pssm-ID: 341442 Cd Length: 137 Bit Score: 222.42 E-value: 4.66e-72
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| Name | Accession | Description | Interval | E-value | |||||
| AP-4_Mu4_Cterm | cd09253 | C-terminal domain of medium Mu4 subunit in adaptor protein (AP) complex AP-4; AP complexes ... |
182-419 | 3.01e-102 | |||||
C-terminal domain of medium Mu4 subunit in adaptor protein (AP) complex AP-4; AP complexes participate in the formation of intracellular coated transport vesicles and select cargo molecules for incorporation into the coated vesicles in the late secretory and endocytic pathways. There are four AP complexes, AP-1, AP-2, AP-3, and AP-4, described in various eukaryotic organisms. Each AP complex consists of four subunits: two large chains (one each of gamma/alpha/delta/epsilon and beta1-4, respectively), a medium mu chain (mu1-4), and a small sigma chain (sigma1-4). Each of the four subunits from the different AP complexes exhibits similarity with each other. This family corresponds to the C-terminal domain of heterotetrameric adaptor protein complex 4 (AP-4) medium mu4 subunit. AP-4 plays a role in signal-mediated trafficking of integral membrane proteins in mammalian cells. Unlike other AP complexes, AP-4 is found only in mammals and plants. It is believed to be part of a nonclathrin coat, since it might function independently of clathrin, a scaffolding protein participating in the formation of coated vesicles. Recruitment of AP-4 to the trans-Golgi network (TGN) membrane is regulated by a small GTPase, ADP-ribosylation factor 1 (ARF1) or a related protein. Membrane-anchored cargo molecules interact with adaptors through short sorting signals in their cytosolic segments. One of the most important sorting signals binding to mu subunits of AP complexes are tyrosine-based endocytotic signals, which are of the form Y-X-X-Phi, where Y is tyrosine, X is any amino acid and Phi is a bulky hydrophobic residue that can be Leu, Ile, Met, Phe, or Val. However, AP-4 does not bind most canonical tyrosine-based signals except for two naturally occurring ones from the lysosomal membrane proteins CD63 and LAMP-2a. It binds YX [FYL][FL]E motif, where X can be any residue, from the cytosolic tails of amyloid precursor protein (APP) family members in a distinct way. Pssm-ID: 271161 Cd Length: 271 Bit Score: 304.49 E-value: 3.01e-102
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| Adap_comp_sub | pfam00928 | Adaptor complexes medium subunit family; This family also contains members which are coatomer ... |
180-419 | 2.25e-72 | |||||
Adaptor complexes medium subunit family; This family also contains members which are coatomer subunits. Pssm-ID: 395742 Cd Length: 259 Bit Score: 227.57 E-value: 2.25e-72
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| AP4_Mu_N | cd14838 | AP-4 complex subunit mu N-terminal domain; AP-4 complex mu subunit is part of the ... |
3-148 | 4.66e-72 | |||||
AP-4 complex subunit mu N-terminal domain; AP-4 complex mu subunit is part of the heterotetrameric adaptor protein (AP)-1 complex which consists of one large epsilon-, one beta-, one mu-, and one sigma-subunit. AP complexes link the cytosolic domains of the cargo proteins to the protein coat that induces vesicle budding in the donor compartment during vesicle transport. AP-4 does not bind the coat protein clathrin, it is associated with nonclathrin coats. Its phospholipid binding partner is unknown and it is localized in the trans-Golgi network (TGN). The mu subunit is comprised of an N-terminal longin domain followed by a C-terminal domain which is involved in the binding of the Y-X-X-Phi sorting signal. Pssm-ID: 341442 Cd Length: 137 Bit Score: 222.42 E-value: 4.66e-72
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| Clat_adaptor_s | pfam01217 | Clathrin adaptor complex small chain; |
64-137 | 6.47e-04 | |||||
Clathrin adaptor complex small chain; Pssm-ID: 460115 Cd Length: 142 Bit Score: 39.65 E-value: 6.47e-04
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| Name | Accession | Description | Interval | E-value | |||||
| AP-4_Mu4_Cterm | cd09253 | C-terminal domain of medium Mu4 subunit in adaptor protein (AP) complex AP-4; AP complexes ... |
182-419 | 3.01e-102 | |||||
C-terminal domain of medium Mu4 subunit in adaptor protein (AP) complex AP-4; AP complexes participate in the formation of intracellular coated transport vesicles and select cargo molecules for incorporation into the coated vesicles in the late secretory and endocytic pathways. There are four AP complexes, AP-1, AP-2, AP-3, and AP-4, described in various eukaryotic organisms. Each AP complex consists of four subunits: two large chains (one each of gamma/alpha/delta/epsilon and beta1-4, respectively), a medium mu chain (mu1-4), and a small sigma chain (sigma1-4). Each of the four subunits from the different AP complexes exhibits similarity with each other. This family corresponds to the C-terminal domain of heterotetrameric adaptor protein complex 4 (AP-4) medium mu4 subunit. AP-4 plays a role in signal-mediated trafficking of integral membrane proteins in mammalian cells. Unlike other AP complexes, AP-4 is found only in mammals and plants. It is believed to be part of a nonclathrin coat, since it might function independently of clathrin, a scaffolding protein participating in the formation of coated vesicles. Recruitment of AP-4 to the trans-Golgi network (TGN) membrane is regulated by a small GTPase, ADP-ribosylation factor 1 (ARF1) or a related protein. Membrane-anchored cargo molecules interact with adaptors through short sorting signals in their cytosolic segments. One of the most important sorting signals binding to mu subunits of AP complexes are tyrosine-based endocytotic signals, which are of the form Y-X-X-Phi, where Y is tyrosine, X is any amino acid and Phi is a bulky hydrophobic residue that can be Leu, Ile, Met, Phe, or Val. However, AP-4 does not bind most canonical tyrosine-based signals except for two naturally occurring ones from the lysosomal membrane proteins CD63 and LAMP-2a. It binds YX [FYL][FL]E motif, where X can be any residue, from the cytosolic tails of amyloid precursor protein (APP) family members in a distinct way. Pssm-ID: 271161 Cd Length: 271 Bit Score: 304.49 E-value: 3.01e-102
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| Adap_comp_sub | pfam00928 | Adaptor complexes medium subunit family; This family also contains members which are coatomer ... |
180-419 | 2.25e-72 | |||||
Adaptor complexes medium subunit family; This family also contains members which are coatomer subunits. Pssm-ID: 395742 Cd Length: 259 Bit Score: 227.57 E-value: 2.25e-72
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| AP4_Mu_N | cd14838 | AP-4 complex subunit mu N-terminal domain; AP-4 complex mu subunit is part of the ... |
3-148 | 4.66e-72 | |||||
AP-4 complex subunit mu N-terminal domain; AP-4 complex mu subunit is part of the heterotetrameric adaptor protein (AP)-1 complex which consists of one large epsilon-, one beta-, one mu-, and one sigma-subunit. AP complexes link the cytosolic domains of the cargo proteins to the protein coat that induces vesicle budding in the donor compartment during vesicle transport. AP-4 does not bind the coat protein clathrin, it is associated with nonclathrin coats. Its phospholipid binding partner is unknown and it is localized in the trans-Golgi network (TGN). The mu subunit is comprised of an N-terminal longin domain followed by a C-terminal domain which is involved in the binding of the Y-X-X-Phi sorting signal. Pssm-ID: 341442 Cd Length: 137 Bit Score: 222.42 E-value: 4.66e-72
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| AP_MHD_Cterm | cd07954 | C-terminal domain of adaptor protein (AP) complexes medium mu subunits and its homologs (MHD); ... |
193-418 | 8.66e-72 | |||||
C-terminal domain of adaptor protein (AP) complexes medium mu subunits and its homologs (MHD); This family corresponds to the C-terminal domain of heterotetrameric AP complexes medium mu subunits and its homologs existing in monomeric stonins, delta-subunit of the heteroheptameric coat protein I (delta-COPI), a protein encoded by a pro-death gene referred as MuD (also known as MUDENG, mu-2 related death-inducing gene), an endocytic adaptor syp1, the mammalian FCH domain only proteins (FCHo1/2), SH3-containing GRB2-like protein 3-interacting protein 1 (SGIP1), and related proteins. AP complexes participate in the formation of intracellular coated transport vesicles and select cargo molecules for incorporation into the coated vesicles in the late secretory and endocytic pathways. Stonins have been characterized as clathrin-dependent AP-2 mu chain related factors and may act as cargo-specific sorting adaptors in endocytosis. Coat protein complex I (COPI)-coated vesicles function in the early secretory pathway. They mediate the retrograde transport from the Golgi to the ER, and intra-Golgi transport. MuD is distantly related to the C-terminal domain of mu2 subunit of AP-2. It is able to induce cell death by itself and plays an important role in cell death in various tissues. Syp1 represents a novel type of endocytic adaptor protein that participates in endocytosis, promotes vesicle tabulation, and contributes to cell polarity and stress responses. It shares the same domain architecture with its two ubiquitously expressed mammalian counterparts, FCHo1/2, which represent key initial proteins ultimately controlling cellular nutrient uptake, receptor regulation, and synaptic vesicle retrieval. They bind specifically to the plasma membrane and recruit the scaffold proteins eps15 and intersectin, which subsequently engage the adaptor complex AP2 and clathrin, leading to coated vesicle formation. Another mammalian neuronal-specific protein SGIP1 does have a C-terminal MHD and has been classified into this family as well. It is an endophilin-interacting protein that plays an obligatory role in the regulation of energy homeostasis. It is also involved in clathrin-mediated endocytosis by interacting with phospholipids and eps15. Pssm-ID: 271157 Cd Length: 245 Bit Score: 225.75 E-value: 8.66e-72
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| AP-2_Mu2_Cterm | cd09251 | C-terminal domain of medium Mu2 subunit in ubiquitously expressed clathrin-associated adaptor ... |
191-418 | 1.09e-44 | |||||
C-terminal domain of medium Mu2 subunit in ubiquitously expressed clathrin-associated adaptor protein (AP) complex AP-2; AP complexes participate in the formation of intracellular coated transport vesicles and select cargo molecules for incorporation into the coated vesicles in the late secretory and endocytic pathways. There are four AP complexes, AP-1, -2, -3, and -4, described in various eukaryotic organisms. Each AP complex consists of four subunits: two large chains (one each of gamma/alpha/delta/epsilon and beta1-4, respectively), a medium mu chain (mu1-4), and a small sigma chain (sigma1-4). Each of the four subunits from the different AP complexes exhibits similarity with each other. This family corresponds to the C-terminal domain of heterotetrameric clathrin-associated adaptor protein complex 2 (AP-2) medium mu2 subunit. Mu2 is ubiquitously expressed in mammals. In higher eukaryotes, AP-2 plays a critical role in clathrin-mediated endocytosis from the plasma membrane in different cells. The membrane-anchored cargo molecules can be linked to the outer lattice of CCVs by AP-2. Those cargo molecules interact with adaptors through short sorting signals in their cytosolic segments. Tyrosine-based endocytotic signals are one of the most important sorting signals. They are of the form Y-X-X-Phi, where Y is tyrosine, X is any amino acid and Phi is a bulky hydrophobic residue that can be Leu, Ile, Met, Phe, or Val. These kinds of sorting signals can be recognized by the C-terminal domain of AP-2 mu2 subunit, also known as Y-X-X-Phi signal-binding domain that contains two hydrophobic pockets, one for the tyrosine-binding and one for the bulky hydrophobic residue-binding. Since the Y-X-X-Phi binding site is buried in the core structure of AP-2, a phosphorylation induced conformational change is required when the cargo molecules binds to AP-2. In addition, the C-terminal domain of mu2 subunit has been shown to bind other molecules. For instance, it can bind phosphoinositides, in particular PI[4,5]P2, which might be involved in the recognition process of the tyrosine-based signals. It can also interact with synaptotagmins, a family of important modulators of calcium-dependent neurosecretion within the synaptic vesicle (SV) membrane. Since many of the other endocytic adaptors responsible for biogenesis of synaptic vesicles exist, in the absence of AP-2, clathrin-mediated endocytosis can still occur. However, the cells may not survive in the complete absence of clathrin as well as AP-2. Pssm-ID: 271159 Cd Length: 263 Bit Score: 155.83 E-value: 1.09e-44
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| AP2_Mu_N | cd14836 | AP-2 complex subunit mu N-terminal domain; AP-2 complex mu subunit is part of the ... |
1-148 | 3.23e-33 | |||||
AP-2 complex subunit mu N-terminal domain; AP-2 complex mu subunit is part of the heterotetrameric adaptor protein (AP)-2 complex which consists of one large alpha-, one beta-, one mu-, and one sigma-subunit. AP complexes link the cytosolic domains of the cargo proteins to the protein coat that induces vesicle budding in the donor compartment during vesicle transport. In the case of AP-2 the coat protein is clathrin. AP-2 binds the phospholipid PI(4,5)P2 which is important for its localisation to the plasma membrane. The mu subunit is comprised of an N-terminal longin domain followed by a C-terminal domain which is involved in the binding of the Y-X-X-Phi sorting signal. Pssm-ID: 341440 Cd Length: 140 Bit Score: 121.48 E-value: 3.23e-33
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| AP_Mu_N | cd14828 | AP complex subunit mu N-terminal domain; AP complex mu subunits are part of the ... |
3-141 | 3.19e-32 | |||||
AP complex subunit mu N-terminal domain; AP complex mu subunits are part of the heterotetrameric adaptor protein (AP) complex which consists of one large subunit (alpha-, gamma-, delta- or epsilon), one beta-, one mu-, and one sigma-subunit. In general, AP complexes link the cytosolic domains of the cargo proteins to the protein coat that induces vesicle budding in the donor compartment during vesicle transport. In most cases the coat protein is clathrin (AP1 and AP2 complex), but some of the other members of the AP complex family are associated with nonclathrin coats. The mu subunit is comprised of an N-terminal longin domain followed by a C-terminal domain which is involved in the binding of the Y-X-X-Phi sorting signal. Pssm-ID: 341432 Cd Length: 136 Bit Score: 118.84 E-value: 3.19e-32
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| AP-1_Mu1_Cterm | cd09250 | C-terminal domain of medium Mu1 subunit in clathrin-associated adaptor protein (AP) complex ... |
191-418 | 2.55e-27 | |||||
C-terminal domain of medium Mu1 subunit in clathrin-associated adaptor protein (AP) complex AP-1; AP complexes participate in the formation of intracellular coated transport vesicles and select cargo molecules for incorporation into the coated vesicles in the late secretory and endocytic pathways. There are four AP complexes, AP-1, AP-2, AP-3, and AP-4, described in various eukaryotic organisms. Each AP complex consists of four subunits: two large chains (one each of gamma/alpha/delta/epsilon and beta1-4, respectively), a medium mu chain (mu1-4), and a small sigma chain (sigma1-4). Each of the four subunits from the different AP complexes exhibits similarity with each other. This family corresponds to the C-terminal domain of heterotetrameric clathrin-associated adaptor protein complex 1 (AP-1) medium mu1 subunit, which includes two closely related homologs, mu1A (encoded by ap1m1) and mu1B (encoded by ap1m2). Mu1A is ubiquitously expressed, but mu1B is expressed exclusively in polarized epithelial cells. AP-1 has been implicated in bi-directional transport between the trans-Golgi network (TGN) and endosomes. It plays an essential role in the formation of clathrin-coated vesicles (CCVs) from the trans-Golgi network (TGN). Epithelial cell-specific AP-1 is also involved in sorting to the basolateral surface of polarized epithelial cells. Recruitment of AP-1 to the TGN membrane is regulated by a small GTPase, ADP-ribosylation factor 1 (ARF1). Phosphorylation/dephosphorylation events can also regulate the function of AP-1. The membrane-anchored cargo molecules can be linked to the outer lattice of CCVs by AP-1. Those cargo molecules interact with adaptors through short sorting signals in their cytosolic segments. Tyrosine-based endocytotic signals are one of the most important sorting signals. They are of the form Y-X-X-Phi, where Y is tyrosine, X is any amino acid and Phi is a bulky hydrophobic residue that can be Leu, Ile, Met, Phe, or Val. These kinds of sorting signals can be recognized by the C-terminal domain of AP-1 mu1 subunit, also known as Y-X-X-Phi signal-binding domain that contains two hydrophobic pockets, one for the tyrosine-binding and one for the bulky hydrophobic residue-binding. Pssm-ID: 271158 Cd Length: 272 Bit Score: 109.61 E-value: 2.55e-27
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| AP1_Mu_N | cd14835 | AP-1 complex subunit mu N-terminal domain; AP-1 complex mu subunit is part of the ... |
3-145 | 9.40e-27 | |||||
AP-1 complex subunit mu N-terminal domain; AP-1 complex mu subunit is part of the heterotetrameric adaptor protein (AP)-1 complex which consists of one large gamma-, one beta-, one mu-, and one sigma-subunit. AP complexes link the cytosolic domains of the cargo proteins to the protein coat that induces vesicle budding in the donor compartment during vesicle transport. In the case of AP-1 the coat protein is clathrin. AP-1 binds the phospholipid PI(4)P which plays a role in its localisation to the trans-Golgi network (TGN)/endosome. The mu subunit is comprised of an N-terminal longin domain followed by a C-terminal domain which is involved in the binding of the Y-X-X-Phi sorting signal. Pssm-ID: 341439 Cd Length: 139 Bit Score: 104.17 E-value: 9.40e-27
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| AP-1_Mu1B_Cterm | cd09259 | C-terminal domain of medium Mu1B subunit in epithelial cell-specific clathrin-associated ... |
182-418 | 2.92e-26 | |||||
C-terminal domain of medium Mu1B subunit in epithelial cell-specific clathrin-associated adaptor protein (AP) complex AP-1; AP complexes participate in the formation of intracellular coated transport vesicles and select cargo molecules for incorporation into the coated vesicles in the late secretory and endocytic pathways. There are four AP complexes, AP-1, AP-2, AP-3, and AP-4, described in various eukaryotic organisms. Each AP complex consists of four subunits: two large chains (one each of gamma/alpha/delta/epsilon and beta1-4, respectively), a medium mu chain (mu1-4), and a small sigma chain (sigma1-4). Each of the four subunits from different AP complexes exhibits similarity with each other. This subfamily corresponds to the C-terminal domain of heterotetrameric clathrin-associated adaptor protein complex 1 (AP-1) medium mu1B subunit encoded by ap1m2 gene exclusively expressed in polarized epithelial cells. Epithelial cell-specific AP-1 is used to sort proteins to the basolateral plasma membrane, which involves the formation of clathrin-coated vesicles (CCVs) from the trans-Golgi network (TGN). Recruitment of AP-1 to the TGN membrane is regulated by a small GTPase, ADP-ribosylation factor 1 (ARF1). The phosphorylation/dephosphorylation events can also regulate the function of AP-1. The membrane-anchored cargo molecules can be linked to the outer lattice of CCVs by AP-1. Those cargo molecules interact with adaptors through short sorting signals in their cytosolic segments. Tyrosine-based endocytotic signals are one of the most important sorting signals. They are of the form Y-X-X-Phi, where Y is tyrosine, X is any amino acid and Phi is a bulky hydrophobic residue that can be Leu, Ile, Met, Phe, or Val. These kinds of sorting signals can be recognized by the C-terminal domain of AP-1 mu1B subunit, also known as Y-X-X-Phi signal-binding domain that contains two hydrophobic pockets, one for the tyrosine-binding and one for the bulky hydrophobic reside-binding. Besides, AP-1 mu1B subunit mediates the basolateral recycling of low-density lipoprotein receptor (LDLR) and transferrin receptor (TfR) from the sorting endosomes, where the basolateral sorting signal does not belong to the tyrosine-based signals. Thus, the binding site in mu1B subunit of AP-1 for the signals of LDLR and TfR might be distinct from that for YXXPhi signals. Pssm-ID: 271167 Cd Length: 268 Bit Score: 106.64 E-value: 2.92e-26
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| AP3_Mu_N | cd14837 | AP-3 complex subunit mu N-terminal domain; AP-3 complex mu subunit is part of the ... |
5-148 | 4.32e-24 | |||||
AP-3 complex subunit mu N-terminal domain; AP-3 complex mu subunit is part of the heterotetrameric adaptor protein (AP)-1 complex which consists of one large delta-, one beta-, one mu-, and one sigma-subunit. AP complexes link the cytosolic domains of the cargo proteins to the protein coat that induces vesicle budding in the donor compartment during vesicle transport. AP-3 binds the coat protein clathrin and the phospholipid PI(3)P and it is localized in the endosome. The mu subunit is comprised of an N-terminal longin domain followed by a C-terminal domain which is involved in the binding of the Y-X-X-Phi sorting signal. Pssm-ID: 341441 Cd Length: 139 Bit Score: 96.82 E-value: 4.32e-24
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| AP-3_Mu3_Cterm | cd09252 | C-terminal domain of medium Mu3 subunit in adaptor protein (AP) complex AP-3; AP complexes ... |
192-374 | 1.06e-23 | |||||
C-terminal domain of medium Mu3 subunit in adaptor protein (AP) complex AP-3; AP complexes participate in the formation of intracellular coated transport vesicles and select cargo molecules for incorporation into the coated vesicles in the late secretory and endocytic pathways. There are four AP complexes, AP-1, AP-2, AP-3, and AP-4, described in various eukaryotic organisms. Each AP complex consists of four subunits: two large chains (one each of gamma/alpha/delta/epsilon and beta1-4, respectively), a medium mu chain (mu1-4), and a small sigma chain (sigma1-4). Each of the four subunits from the different AP complexes exhibits similarity with each other. This family corresponds to the C-terminal domain of heterotetrameric adaptor protein complex 3 (AP-3) medium mu3 subunit, which includes two closely related homologs, mu3A (P47A, encoded by ap3m1) and mu1B (P47B, encoded by ap3m2). Mu3A is ubiquitously expressed, but mu3B is specifically expressed in neurons and neuroendocrine cells. AP-3 is particularly important for targeting integral membrane proteins to lysosomes and lysome-related organelles at trans-Golgi network (TGN) and/or endosomes, such as the yeast vacuole, fly pigment granules and mammalian melanosomes, platelet dense bodies and the secretory lysosomes of cytotoxic T lymphocytes. Unlike AP-1 and AP-2, which function in conjunction with clathrin which is a scaffolding protein participating in the formation of coated vesicles, the nature of the outer shell of AP-3 containing coats remains to be elucidated. Membrane-anchored cargo molecules interact with adaptors through short sorting signals in their cytosolic segments. Tyrosine-based endocytotic signals are one of the most important sorting signals. They are of the form Y-X-X-Phi, where Y is tyrosine, X is any amino acid and Phi is a bulky hydrophobic residue that can be Leu, Ile, Met, Phe, or Val. These kinds of sorting signals can be recognized by the C-terminal domain of AP-3 mu3 subunit, also known as Y-X-X-Phi signal-binding domain that contains two hydrophobic pockets, one for the tyrosine-binding and one for the bulky hydrophobic residue-binding. Pssm-ID: 271160 Cd Length: 251 Bit Score: 99.20 E-value: 1.06e-23
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| AP-1_Mu1A_Cterm | cd09258 | C-terminal domain of medium Mu1A subunit in ubiquitously expressed clathrin-associated adaptor ... |
182-418 | 1.68e-22 | |||||
C-terminal domain of medium Mu1A subunit in ubiquitously expressed clathrin-associated adaptor protein (AP) complex AP-1; AP complexes participate in the formation of intracellular coated transport vesicles and select cargo molecules for incorporation into the coated vesicles in the late secretory and endocytic pathways. There are four AP complexes, AP-1, AP-2, AP-3, and AP-4, described in various eukaryotic organisms. Each AP complex consists of four subunits: two large chains (one each of gamma/alpha/delta/epsilon and beta1-4, respectively), a medium mu chain (mu1-4), and a small sigma chain (sigma1-4). Each of the four subunits from the different AP complexes exhibits similarity with each other. This subfamily corresponds to the C-terminal domain of heterotetrameric clathrin-associated adaptor protein complex 1 (AP-1) medium mu1A subunit encoded by ap1m1 gene, which is ubiquitously expressed in all mammalian tissues and cells. AP-1 has been implicated in bidirectional transport between the trans-Golgi network (TGN) and endosomes. It is involved in the formation of clathrin-coated vesicles (CCVs) from the trans-Golgi network (TGN). The ubiquitous AP-1 is recruited to the TGN membrane, as well as to immature secretory granules. Recruitment of AP-1 to the TGN membrane is regulated by a small GTPase, ADP-ribosylation factor 1 (ARF1). Phosphorylation/dephosphorylation events can also regulate the function of AP-1. The membrane-anchored cargo molecules can be linked to the outer lattice of CCVs by AP-1. Those cargo molecules interact with adaptors through short sorting signals in their cytosolic segments. Tyrosine-based endocytotic signals are one of the most important sorting signals. They are of the form Y-X-X-Phi, where Y is tyrosine, X is any amino acid and Phi is a bulky hydrophobic residue that can be Leu, Ile, Met, Phe, or Val. These kinds of sorting signals can be recognized by the C-terminal domain of AP-1 mu1A subunit, also known as Y-X-X-Phi signal-binding domain that contains two hydrophobic pockets, one for the tyrosine-binding and one for the bulky hydrophobic residue-binding. Pssm-ID: 271166 Cd Length: 270 Bit Score: 96.10 E-value: 1.68e-22
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| AP_longin-like | cd14823 | Longin-like domains of AP complex subunits; AP complex sigma subunits are part of the ... |
6-140 | 9.37e-15 | |||||
Longin-like domains of AP complex subunits; AP complex sigma subunits are part of the heterotetrameric adaptor protein (AP) complex which consists of one large subunit (alpha-, gamma-, delta- or epsilon), one beta-, one mu-, and one sigma-subunit. In general, AP complexes link the cytosolic domains of the cargo proteins to the protein coat that induces vesicle budding in the donor compartment during vesicle transport. In most cases the coat protein is clathrin (AP1 and AP2 complex), but some of the other members of the AP complex family are associated with nonclathrin coats. The sigma subunit is comprised of a single longin domain and plays a role in binding dileucine-based sorting signals. Pssm-ID: 341427 Cd Length: 131 Bit Score: 70.62 E-value: 9.37e-15
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| AP-like_stonins_MHD | cd09255 | Mu homology domain (MHD) of adaptor-like proteins (AP-like), stonins; A small family of ... |
191-392 | 2.62e-14 | |||||
Mu homology domain (MHD) of adaptor-like proteins (AP-like), stonins; A small family of proteins named stonins has been characterized as clathrin-dependent AP-2 mu2 chain related factors, which may act as cargo-specific sorting adaptors in endocytosis. Stonins include stonin 1 and stonin 2, which are only mammalian homologs of Drosophila stoned B, a presynaptic protein implicated in neurotransmission and synaptic vesicle (SV) recycling. They are conserved from C. elegans to humans, but are not found in prokaryotes or yeasts. This family corresponds to the mu homology domain of stonins, which is distantly related to the C-terminal domain of mu chains among AP complexes. Due to the low degree of sequence conservation of the corresponding binding site, the mu homology domain of stonins is unable to recognize tyrosine-based endocytic sorting signals. To data, little is known about the localization and function of stonin 1. Stonin 2, also known as stoned B, acts as an AP-2-dependent synaptotagmin-specific sorting adaptors for SV endocytosis. Stoned A is not a stonin. It is structurally unrelated to the adaptins and does not appear to have mammalian homologs. It is not included in this family. Pssm-ID: 271163 [Multi-domain] Cd Length: 315 Bit Score: 73.21 E-value: 2.62e-14
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| AP-3_Mu3B_Cterm | cd09261 | C-terminal domain of medium Mu3B subunit in neuron-specific adaptor protein (AP) complex AP-3; ... |
192-375 | 7.01e-10 | |||||
C-terminal domain of medium Mu3B subunit in neuron-specific adaptor protein (AP) complex AP-3; AP complexes participate in the formation of intracellular coated transport vesicles and select cargo molecules for incorporation into the coated vesicles in the late secretory and endocytic pathways. There are four AP complexes, AP-1, AP-2, AP-3, and AP-4, described in various eukaryotic organisms. Each AP complex consists of four subunits: two large chains (one each of gamma/alpha/delta/epsilon and beta1-4, respectively), a medium mu chain (mu1-4), and a small sigma chain (sigma1-4). Each of the four subunits from the different AP complexes exhibits similarity with each other. This subfamily corresponds to the C-terminal domain of heterotetrameric adaptor protein complex 3 (AP-3) medium mu3B subunit encoded by ap3m2 gene. Mu3B is specifically expressed in neurons and neuroendocrine cells. Neuron-specific AP-3 appears to be involved in synaptic vesicle biogenesis from endosomes in neurons and plays an important role in synaptic transmission in the central nervous system. Unlike AP-1 and AP-2, which function in conjunction with clathrin which is a scaffolding protein participating in the formation of coated vesicles, the nature of the outer shell of neuron-specific AP-3 containing coats remains to be elucidated. Membrane-anchored cargo molecules interact with adaptors through short sorting signals in their cytosolic segments. Tyrosine-based endocytotic signals are one of the most important sorting signals. They are of the form Y-X-X-Phi, where Y is tyrosine, X is any amino acid and Phi is a bulky hydrophobic residue that can be Leu, Ile, Met, Phe, or Val. These kinds of sorting signals can be recognized by the C-terminal domain of AP-3 mu3B subunit, also known as Y-X-X-Phi signal-binding domain that contains two hydrophobic pockets, one for the tyrosine-binding and one for the bulky hydrophobic residue-binding. Pssm-ID: 211372 Cd Length: 254 Bit Score: 59.28 E-value: 7.01e-10
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| AP-3_Mu3A_Cterm | cd09260 | C-terminal domain of medium Mu3A subunit in ubiquitously expressed adaptor protein (AP) ... |
192-388 | 3.04e-09 | |||||
C-terminal domain of medium Mu3A subunit in ubiquitously expressed adaptor protein (AP) complex AP-3; AP complexes participate in the formation of intracellular coated transport vesicles and select cargo molecules for incorporation into the coated vesicles in the late secretory and endocytic pathways. There are four AP complexes, AP-1, AP-2, AP-3, and AP-4, described in various eukaryotic organisms. Each AP complex consists of four subunits: two large chains (one each of gamma/alpha/delta/epsilon and beta1-4, respectively), a medium mu chain (mu1-4), and a small sigma chain (sigma1-4). Each of the four subunits from the different AP complexes exhibits similarity with each other. This subfamily corresponds to the C-terminal domain of heterotetrameric adaptor protein complex 3 (AP-3) medium mu3A subunit encoded by ap3m1gene. Mu3A is ubiquitously expressed in all mammalian tissues and cells. It appears to be localized to the trans-Golgi network (TGN) and/or endosomes and participates in trafficking to the vacuole/lysosome in yeast, flies, and mammals. Unlike AP-1 and AP-2, which function in conjunction with clathrin which is a scaffolding protein participating in the formation of coated vesicles, the nature of the outer shell of ubiquitous AP-3 containing coats remains to be elucidated. Membrane-anchored cargo molecules interact with adaptors through short sorting signals in their cytosolic segments. Tyrosine-based endocytotic signals are one of the most important sorting signals. They are of the form Y-X-X-Phi, where Y is tyrosine, X is any amino acid and Phi is a bulky hydrophobic residue that can be Leu, Ile, Met, Phe, or Val. These kinds of sorting signals can be recognized by the C-terminal domain of AP-3 mu3A subunit, also known as Y-X-X-Phi signal-binding domain that contains two hydrophobic pockets, one for the tyrosine-binding and one for the bulky hydrophobic residue-binding. Pssm-ID: 211371 Cd Length: 254 Bit Score: 57.42 E-value: 3.04e-09
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| AP_stonin-1_MHD | cd09262 | Mu homology domain (MHD) of adaptor-like protein (AP-like), stonin-1 (also called Stoned ... |
190-361 | 8.77e-06 | |||||
Mu homology domain (MHD) of adaptor-like protein (AP-like), stonin-1 (also called Stoned B-like factor); A small family of proteins named stonins has been characterized as clathrin-dependent AP-2 mu2 chain related factors, which may act as cargo-specific sorting adaptors in endocytosis. Stonins include stonin 1 and stonin 2, which are the only mammalian homologs of Drosophila stoned B, a presynaptic protein implicated in neurotransmission and synaptic vesicle (SV) recycling. They are conserved from C. elegans to humans, but are not found in prokaryotes or yeasts. This family corresponds to the mu homology domain of stonin 1, which is distantly related to the C-terminal domain of mu chains among AP complexes. Due to the low degree of sequence conservation of the corresponding binding site, the mu homology domain of stonin-1 is unable to recognize tyrosine-based endocytic sorting signals. To data, little is known about the localization and function of stonin-1. Pssm-ID: 271168 Cd Length: 314 Bit Score: 47.24 E-value: 8.77e-06
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| Clat_adaptor_s | pfam01217 | Clathrin adaptor complex small chain; |
64-137 | 6.47e-04 | |||||
Clathrin adaptor complex small chain; Pssm-ID: 460115 Cd Length: 142 Bit Score: 39.65 E-value: 6.47e-04
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| Delta_COP_N | cd14830 | delta subunit of the F-COPI complex, N-terminal domain; Delta subunit of the heterotetrameric ... |
71-140 | 7.31e-04 | |||||
delta subunit of the F-COPI complex, N-terminal domain; Delta subunit of the heterotetrameric F-COPI complex, which consists of one beta-, one gamma-, one delta-, and one zeta subunit, where beta- and gamma- subunits are related to the large adaptor protein (AP) complex subunits, and delta- and zeta- subunits are related to the medium and small AP subunits, respectively. F-COPI forms a coatomer together with the B-COPI subcomplex, which assembles with a small GTPase, ADP-ribosylation factor 1 (ARF1), playing an important role in the formation of COPI complex-coated vesicles. COPI complex-coated vesicles function in the early secretory pathway mediating the retrograde transport from the Golgi to the ER, and intra-Golgi transport. Pssm-ID: 341434 Cd Length: 130 Bit Score: 39.43 E-value: 7.31e-04
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| AP_stonin-2_MHD | cd09263 | Mu homology domain (MHD) of adaptor-like protein (AP-like), stonin-2; A small family of ... |
190-344 | 8.03e-04 | |||||
Mu homology domain (MHD) of adaptor-like protein (AP-like), stonin-2; A small family of proteins named stonins has been characterized as clathrin-dependent AP-2 mu2 chain related factors, which may act as cargo-specific sorting adaptors in endocytosis. Stonins include stonin 1 and stonin 2, which are the only mammalian homologs of Drosophila stoned B, a presynaptic protein implicated in neurotransmission and synaptic vesicle (SV) recycling. They are conserved from C. elegans to humans, but are not found in prokaryotes or yeasts. This family corresponds to the mu homology domain of stonin 2, which is distantly related to the C-terminal domain of mu chains among AP complexes. Due to the low degree of sequence conservation of the corresponding binding site, the mu homology domain of stonin-2 is unable to recognize tyrosine-based endocytic sorting signals. It acts as an AP-2-dependent synaptotagmin-specific sorting adaptor for SV endocytosis. Pssm-ID: 271169 Cd Length: 318 Bit Score: 41.16 E-value: 8.03e-04
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| AP_Syp1_like_MHD | cd09265 | Mu-homology domain (MHD) of endocytic adaptor protein (AP), Syp1; This family corresponds to ... |
288-383 | 2.12e-03 | |||||
Mu-homology domain (MHD) of endocytic adaptor protein (AP), Syp1; This family corresponds to the MHD found in the metazoan counterparts of yeast Syp1, which includes two ubiquitously expressed membrane-sculpting F-BAR domain-containing Fer/Cip4 homology domain-only proteins 1 and 2 (FCH domain only 1 and 2, or FCHo1/FCHo2), neuronal-specific SH3-containing GRB2-like protein 3-interacting protein 1 (SGIP1), and related uncharacterized proteins. FCHo1/FCHo2 represent key initial proteins ultimately controlling cellular nutrient uptake, receptor regulation, and synaptic vesicle retrieval. They are required for plasma membrane clathrin-coated vesicle (CCV) budding and marked sites of CCV formation. They bind specifically to the plasma membrane and recruit the scaffold proteins eps15 and intersectin, which subsequently engage the adaptor complex AP2 and clathrin, leading to coated vesicle formation. Both FCHo1/FCHo2 contain an N-terminal EFC/F-BAR domain that induces membrane tabulation, a proline-rich domain (PRD) in the middle region, and a C-terminal MHD responsible for the binding of eps15 and intersectin. Another mammalian neuronal-specific protein, neuronal-specific transcript Scr homology 3 (SH3)-domain growth factor receptor-bound 2 (GRB2)-like (endophilin) interacting protein 1 [SGIP1] does not contain EFC/F-BAR domain, but does have a PRD and a C-terminal MHD and has been classified into this family as well. SGIP1 is an endophilin-interacting protein that plays an obligatory role in the regulation of energy homeostasis. It is also involved in clathrin-mediated endocytosis by interacting with phospholipids and eps15. Pssm-ID: 271171 Cd Length: 266 Bit Score: 39.78 E-value: 2.12e-03
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| FCHo1_MHD | cd09268 | mu-homology domain (MHD) of F-BAR domain-containing Fer/Cip4 homology domain-only protein 1 ... |
280-383 | 2.44e-03 | |||||
mu-homology domain (MHD) of F-BAR domain-containing Fer/Cip4 homology domain-only protein 1 (FCH domain only 1 or FCHo1, also known as KIAA0290) and similar proteins; This family corresponds to the MHD found in ubiquitously expressed mammalian membrane-sculpting FCHo1 and similar proteins. FCHo1 represents a key initial protein that ultimately controls cellular nutrient uptake, receptor regulation, and synaptic vesicle retrieval. It is required for plasma membrane clathrin-coated vesicle (CCV) budding and marks sites of CCV formation. It binds specifically to the plasma membrane and recruits the scaffold proteins eps15 and intersectin, which subsequently engage the adaptor complex AP2 and clathrin, leading to coated vesicle formation. FCHo1 contains an N-terminal EFC/F-BAR domain, a proline-rich domain (PRD) in the middle region, and a C-terminal MHD. The crescent-shaped EFC/F-BAR domain can form an antiparallel dimer structure that binds PtdIns(4,5)P2-enriched membranes and can polymerize into rings to generate membrane tubules. The MHD is structurally related to the cargo-binding mu2 subunit of adaptor complex 2 (AP-2) and is responsible for the binding of eps15 and intersectin. Unlike other F-BAR domain containing proteins, FCHo1 has neither the Src homology 3 (SH3) domain nor any other known domain for interaction with dynamin and actin cytoskeleton. However, it can periodically accumulate at the budding site of clathrin. FCHo1 may utilize a unique action mode for vesicle formation as compared with other F-BAR proteins. Pssm-ID: 271173 Cd Length: 265 Bit Score: 39.56 E-value: 2.44e-03
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| AP_delta-COPI_MHD | cd09254 | Mu homology domain (MHD) of adaptor protein (AP) coat protein I (COPI) delta subunit; COPI ... |
194-346 | 7.83e-03 | |||||
Mu homology domain (MHD) of adaptor protein (AP) coat protein I (COPI) delta subunit; COPI complex-coated vesicles function in the early secretory pathway. They mediate the retrograde transport from the Golgi to the ER, and intra-Golgi transport. COPI complex-coated vesicles consist of a small GTPase, ADP-ribosylation factor 1 (ARF1) and a heteroheptameric coatomer composed of two subcomplexes, F-COPI and B-COPI. ARF1 regulates COPI vesicle formation by recruiting the coatomer onto Golgi membranes to initiate its coat function. Coatomer complexes then bind cargo molecules and self-assemble to form spherical cages that yield COPI-coated vesicles. The heterotetrameric F-COPI subcomplex contains beta-, gamma-, delta-, and zeta-COP subunits, where beta- and gamma-COP subunits are related to the large AP subunits, and delta- and zeta-COP subunits are related to the medium and small AP subunits, respectively. Due to the sequence similarity to the AP complexes, the F-COPI subcomplex might play a role in the cargo-binding. The heterotrimeric B-COPI contains alpha-, beta-, and epsilon-COP subunits, which are not related to the adaptins. This subcomplex is thought to participate in the cage-forming and might serve a function similar to that of clathrin. This family corresponds to the mu homology domain of delta-subunit of COPI complex (delta-COP), which is distantly related to the C-terminal domain of mu chains among AP complexes. The delta-COP subunit appears tightly associated with the beta-COP subunit to confer its interaction with ARF1. In addition, both delta- and beta-COP subunits contribute to a common binding site for arginine (R)-based signals, which are sorting motifs conferring transient endoplasmic reticulum (ER) localization to unassembled subunits of multimeric membrane proteins. Pssm-ID: 271162 Cd Length: 237 Bit Score: 37.59 E-value: 7.83e-03
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