RING finger (Really Interesting New Gene) domain and U-box domain superfamily; The RING finger is a specialized type of Zn-finger of 40 to 60 residues that binds two atoms of zinc. It is defined by the "cross-brace" motif that chelates zinc atoms by eight amino acid residues, typically Cys or His, arranged in a characteristic spacing. Canonical RING motifs have been categorized into two major subclasses, RING-HC (C3HC4-type) and RING-H2 (C3H2C3-type), according to their Cys/His content. There are also many variants of RING fingers: some have different Cys/His patterns while some lack a single Cys or His residue at typical Zn ligand positions (the fourth or eighth zinc ligand is prevalently exchanged for an Asp, which can indeed chelate Zn in a RING finger as well). C4C4-, C3HC3D-, C2H2C4-, and C3HC5-type RING fingers are closely related to RING-HC fingers. In contrast, C4HC3- (RING-CH alias RINGv), C3H3C2-, C3H2C2D-, C3DHC3-, and C4HC2H-type RING fingers are more closely related to RING-H2 fingers. However, not all RING finger-containing proteins display regular RING finger features, and the RING finger family has turned out to be multifarious. The degenerate RING fingers of the Siz/PIAS RING (SP-RING) family proteins and sporulation protein RMD5, are characterized by lacking the second, fifth, and sixth Zn2+ ion-coordinating residues. They bind only one Zn2+ ion. On the other hand, the RING fingers of the human APC11 and RBX1 proteins can bind a third Zn atom since they harbor four additional Zn ligands. U-box is a modified form of the RING finger domain that lacks metal chelating Cys and His residues. It resembles the cross-brace RING structure consisting of three beta-sheets and a single alpha-helix, which would be stabilized by salt bridges instead of chelated metal ions. U-box proteins are widely distributed among eukaryotic organisms and show a higher prevalence in plants than in other organisms. RING finger/U-box-containing proteins are a group of diverse proteins with a variety of cellular functions, including oncogenesis, development, viral replication, signal transduction, the cell cycle and apoptosis. Many of them are ubiquitin-protein ligases (E3s) that serve as scaffolds for binding to ubiquitin-conjugating enzymes (E2s, also referred to as ubiquitin carrier proteins or UBCs) in close proximity to substrate proteins, which enable efficient transfer of ubiquitin from E2 to the substrates.

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gi 1958799565   1 MMMKPSCSWCKDYEQFEENKQLSILVNCYKKLCEYIT 37
Cdd:pfam16685  34 KRLKPSCSWCKDYSQYEENKQLRILLQCYKKLCEYLT 70

DNA-binding cysteine-rich domain of male-specific lethal 2 and related proteins; The CXC domain of Drosophila melanogaster MSL2 forms a Zn(3)Cys(9) cluster and is involved in recruiting members of the dosage compensation complex (DCC) to sites on the X chromosome.

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gi 1958799565 382 PQEKKGCKCGRATQNPSVLTCRGQRCPCYSNRKACLDCICRGCQNSYMAN 431
Cdd:cd13122     1 PPEKKGCRCGTATQSPGVLTCRGQRCPCYSNGKSCLDCKCRGCKNPHKAD 50

RING finger found in Drosophila melanogaster male-specific lethal-2 (MSL2) and similar proteins; MSL2, also known as RING finger protein 184 (RNF184), is a putative DNA-binding protein required for X chromosome dosage compensation in Drosophila males. Its expression is sex specifically regulated by Sex-lethal. Drosophila dosage compensation proteins MOF, MSL1, MSL2, and MSL3 are essential for elevating transcription of the single X chromosome in the male (X chromosome dosage compensation). MSL2 plays a critical role in translation and/or stability of MSL1 in males. In complex with MSL1, it acts as an E3 ubiquitin ligase that promotes ubiquitination of histone H2B. MSL2 contains a C3HC4-type RING-HC finger and a metallothionein-like domain with eight conserved and two non-conserved cysteines, as well as a positively and a negatively charged amino acid residue cluster and a coiled coil domain that may be involved in protein-protein interactions. This subfamily also includes many male-specific lethal-2 homologs from bilaterians.

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gi 1958799565   1 MMMKPSCSWCKDYEQFEENKQL 22
Cdd:cd16522    39 MRLKPSCSWCKDYSQFEENKQL 60

DNA-binding cysteine-rich domain of male-specific lethal 2 and related proteins; The CXC domain of Drosophila melanogaster MSL2 forms a Zn(3)Cys(9) cluster and is involved in recruiting members of the dosage compensation complex (DCC) to sites on the X chromosome.

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gi 1958799565 382 PQEKKGCKCGRATQNPSVLTCRGQRCPCYSNRKACLDCICRGCQNSYMAN 431
Cdd:cd13122     1 PPEKKGCRCGTATQSPGVLTCRGQRCPCYSNGKSCLDCKCRGCKNPHKAD 50

RING finger found in Drosophila melanogaster male-specific lethal-2 (MSL2) and similar proteins; MSL2, also known as RING finger protein 184 (RNF184), is a putative DNA-binding protein required for X chromosome dosage compensation in Drosophila males. Its expression is sex specifically regulated by Sex-lethal. Drosophila dosage compensation proteins MOF, MSL1, MSL2, and MSL3 are essential for elevating transcription of the single X chromosome in the male (X chromosome dosage compensation). MSL2 plays a critical role in translation and/or stability of MSL1 in males. In complex with MSL1, it acts as an E3 ubiquitin ligase that promotes ubiquitination of histone H2B. MSL2 contains a C3HC4-type RING-HC finger and a metallothionein-like domain with eight conserved and two non-conserved cysteines, as well as a positively and a negatively charged amino acid residue cluster and a coiled coil domain that may be involved in protein-protein interactions. This subfamily also includes many male-specific lethal-2 homologs from bilaterians.

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gi 1958799565   1 MMMKPSCSWCKDYEQFEENKQL 22
Cdd:cd16522    39 MRLKPSCSWCKDYSQFEENKQL 60