Heme-copper oxidase subunit I. Heme-copper oxidases are transmembrane protein complexes in the respiratory chains of prokaryotes and mitochondria which catalyze the reduction of O2 and simultaneously pump protons across the membrane. The superfamily is diverse in terms of electron donors, subunit composition, and heme types. The number of subunits varies from three to five in bacteria and up to 13 in mammalian mitochondria. It has been proposed that Archaea acquired heme-copper oxidases through gene transfer from Gram-positive bacteria. Membership in the superfamily is defined by subunit I, which contains a heme-copper binuclear center (the active site where O2 is reduced to water) formed by a high-spin heme and a copper ion. It also contains a low-spin heme, believed to participate in the transfer of electrons to the binuclear center. Only subunit I is common to the entire superfamily. For every reduction of an O2 molecule, eight protons are taken from the inside aqueous compartment and four electrons are taken from the electron donor on the opposite side of the membrane. The four electrons and four of the protons are used in the reduction of O2; the four remaining protons are pumped across the membrane. This charge separation of four charges contributes to the electrochemical gradient used for ATP synthesis. Two proton channels, the D-pathway and K-pathway, leading to the binuclear center have been identified in subunit I of cytochrome c oxidase (CcO) and ubiquinol oxidase. A well-defined pathway for the transfer of pumped protons beyond the binuclear center has not been identified. Electron transfer occurs in two segments: from the electron donor to the low-spin heme, and from the low-spin heme to the binuclear center. The first segment can be a multi-step process and varies among the different families, while the second segment, a direct transfer, is consistent throughout the superfamily.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2087301634   1 SGPGSMLGDDQLYNVAVTAHGLIMIFFFVMPVLLGGFGNWLVPLYIGAPDMAFPRLNNISFWLLPPALLLLLGSSLVEQG 80
Cdd:cd01663    33 SQPGSQLGNDQLYNVIVTAHALIMIFFMVMPALIGGFGNWLVPLMIGAPDMAFPRLNNLSFWLLPPSLLLLLLSALVEGG 112

                  ..
gi 2087301634  81 AG 82
Cdd:cd01663   113 AG 114

Cytochrome C oxidase subunit I. Cytochrome c oxidase (CcO), the terminal oxidase in the respiratory chains of eukaryotes and most bacteria, is a multi-chain transmembrane protein located in the inner membrane of mitochondria and the cell membrane of prokaryotes. It catalyzes the reduction of O2 and simultaneously pumps protons across the membrane. The number of subunits varies from three to five in bacteria and up to 13 in mammalian mitochondria. Only subunits I and II are essential for function, but subunit III, which is also conserved, may play a role in assembly or oxygen delivery to the active site. Subunits I, II, and III of mammalian CcO are encoded within the mitochondrial genome and the remaining 10 subunits are encoded within the nuclear genome. Subunit I contains a heme-copper binuclear center (the active site where O2 is reduced to water) formed by a high-spin heme (heme a3) and a copper ion (CuB). It also contains a low-spin heme (heme a), believed to participate in the transfer of electrons to the binuclear center. For every reduction of an O2 molecule, eight protons are taken from the inside aqueous compartment and four electrons are taken from cytochrome c on the opposite side of the membrane. The four electrons and four of the protons are used in the reduction of O2; the four remaining protons are pumped across the membrane. This charge separation of four charges contributes to the electrochemical gradient used for ATP synthesis. Two proton channels, the D-pathway and K-pathway, leading to the binuclear center have been identified in subunit I. A well-defined pathway for the transfer of pumped protons beyond the binuclear center has not been identified. Electrons are transferred from cytochrome c (the electron donor) to heme a via the CuA binuclear site in subunit II, and directly from heme a to the binuclear center.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2087301634   1 SGPGSMLGDDQLYNVAVTAHGLIMIFFFVMPVLLGGFGNWLVPLYIGAPDMAFPRLNNISFWLLPPALLLLLGSSLVEQG 80
Cdd:cd01663    33 SQPGSQLGNDQLYNVIVTAHALIMIFFMVMPALIGGFGNWLVPLMIGAPDMAFPRLNNLSFWLLPPSLLLLLLSALVEGG 112

                  ..
gi 2087301634  81 AG 82
Cdd:cd01663   113 AG 114

Heme/copper-type cytochrome/quinol oxidase, subunit 1 [Energy production and conversion];

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 2087301634   2 GPGSMLGDDQLYNVAVTAHGLIMIFFFVMPvLLGGFGNWLVPLYIGAPDMAFPRLNNISFW 62
Cdd:COG0843    46 GPGLGLLSPETYNQLFTMHGTIMIFFFATP-FLAGFGNYLVPLQIGARDMAFPRLNALSFW 105

Cytochrome C oxidase subunit I. Cytochrome c oxidase (CcO), the terminal oxidase in the respiratory chains of eukaryotes and most bacteria, is a multi-chain transmembrane protein located in the inner membrane of mitochondria and the cell membrane of prokaryotes. It catalyzes the reduction of O2 and simultaneously pumps protons across the membrane. The number of subunits varies from three to five in bacteria and up to 13 in mammalian mitochondria. Only subunits I and II are essential for function, but subunit III, which is also conserved, may play a role in assembly or oxygen delivery to the active site. Subunits I, II, and III of mammalian CcO are encoded within the mitochondrial genome and the remaining 10 subunits are encoded within the nuclear genome. Subunit I contains a heme-copper binuclear center (the active site where O2 is reduced to water) formed by a high-spin heme (heme a3) and a copper ion (CuB). It also contains a low-spin heme (heme a), believed to participate in the transfer of electrons to the binuclear center. For every reduction of an O2 molecule, eight protons are taken from the inside aqueous compartment and four electrons are taken from cytochrome c on the opposite side of the membrane. The four electrons and four of the protons are used in the reduction of O2; the four remaining protons are pumped across the membrane. This charge separation of four charges contributes to the electrochemical gradient used for ATP synthesis. Two proton channels, the D-pathway and K-pathway, leading to the binuclear center have been identified in subunit I. A well-defined pathway for the transfer of pumped protons beyond the binuclear center has not been identified. Electrons are transferred from cytochrome c (the electron donor) to heme a via the CuA binuclear site in subunit II, and directly from heme a to the binuclear center.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2087301634   1 SGPGSMLGDDQLYNVAVTAHGLIMIFFFVMPVLLGGFGNWLVPLYIGAPDMAFPRLNNISFWLLPPALLLLLGSSLVEQG 80
Cdd:cd01663    33 SQPGSQLGNDQLYNVIVTAHALIMIFFMVMPALIGGFGNWLVPLMIGAPDMAFPRLNNLSFWLLPPSLLLLLLSALVEGG 112

                  ..
gi 2087301634  81 AG 82
Cdd:cd01663   113 AG 114

cytochrome c oxidase subunit I; Provisional

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2087301634   1 SGPGSMLGDDQLYNVAVTAHGLIMIFFFVMPVLLGGFGNWLVPLYIGAPDMAFPRLNNISFWLLPPALLLLLGSSLVEQG 80
Cdd:MTH00167   42 SQPGSLLGDDQIYNVIVTAHAFVMIFFMVMPIMIGGFGNWLVPLMIGAPDMAFPRMNNMSFWLLPPSLLLLLASSGVEAG 121

                  ..
gi 2087301634  81 AG 82
Cdd:MTH00167  122 AG 123

cytochrome c oxidase subunit I; Provisional

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2087301634   1 SGPGSMLGDDQLYNVAVTAHGLIMIFFFVMPVLLGGFGNWLVPLYIGAPDMAFPRLNNISFWLLPPALLLLLGSSLVEQG 80
Cdd:MTH00116   42 GQPGTLLGDDQIYNVIVTAHAFVMIFFMVMPIMIGGFGNWLVPLMIGAPDMAFPRMNNMSFWLLPPSFLLLLASSTVEAG 121

                  ..
gi 2087301634  81 AG 82
Cdd:MTH00116  122 AG 123

cytochrome c oxidase subunit I; Provisional

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2087301634   1 SGPGSMLGDDQLYNVAVTAHGLIMIFFFVMPVLLGGFGNWLVPLYIGAPDMAFPRLNNISFWLLPPALLLLLGSSLVEQG 80
Cdd:MTH00182   44 SAPGAMLGDDHLYNVIVTAHAFIMIFFLVMPVMIGGFGNWLVPLYIGAPDMAFPRLNNISFWLLPPALILLLGSAFVEQG 123

                  ..
gi 2087301634  81 AG 82
Cdd:MTH00182  124 AG 125

cytochrome c oxidase subunit I; Provisional

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2087301634   1 SGPGSMLGDDQLYNVAVTAHGLIMIFFFVMPVLLGGFGNWLVPLYIGAPDMAFPRLNNISFWLLPPALLLLLGSSLVEQG 80
Cdd:MTH00077   42 SQPGTLLGDDQIYNVIVTAHAFVMIFFMVMPIMIGGFGNWLVPLMIGAPDMAFPRMNNMSFWLLPPSFLLLLASSGVEAG 121

                  ..
gi 2087301634  81 AG 82
Cdd:MTH00077  122 AG 123

cytochrome c oxidase subunit I; Validated

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2087301634   3 PGSMLGDDQLYNVAVTAHGLIMIFFFVMPVLLGGFGNWLVPLYIGAPDMAFPRLNNISFWLLPPALLLLLGSSLVEQGAG 82
Cdd:MTH00103   44 PGTLLGDDQIYNVIVTAHAFVMIFFMVMPIMIGGFGNWLVPLMIGAPDMAFPRMNNMSFWLLPPSFLLLLASSMVEAGAG 123

cytochrome c oxidase subunit I; Validated

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2087301634   1 SGPGSMLGDDQLYNVAVTAHGLIMIFFFVMPVLLGGFGNWLVPLYIGAPDMAFPRLNNISFWLLPPALLLLLGSSLVEQG 80
Cdd:MTH00007   39 GQPGAFLGSDQLYNTIVTAHAFLMIFFLVMPVFIGGFGNWLVPLMLGAPDMAFPRLNNMSFWLLPPALILLVSSAAVEKG 118

                  ..
gi 2087301634  81 AG 82
Cdd:MTH00007  119 VG 120

cytochrome c oxidase subunit I; Provisional

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2087301634   1 SGPGSMLGDDQLYNVAVTAHGLIMIFFFVMPVLLGGFGNWLVPLYIGAPDMAFPRLNNISFWLLPPALLLLLGSSLVEQG 80
Cdd:MTH00079   43 SKPGLLLGNGQLYNSVITAHAILMIFFMVMPSMIGGFGNWMLPLMLGAPDMSFPRLNNLSFWLLPTSLFLILDSCFVDMG 122

                  ..
gi 2087301634  81 AG 82
Cdd:MTH00079  123 PG 124

Heme/copper-type cytochrome/quinol oxidase, subunit 1 [Energy production and conversion];

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 2087301634   2 GPGSMLGDDQLYNVAVTAHGLIMIFFFVMPvLLGGFGNWLVPLYIGAPDMAFPRLNNISFW 62
Cdd:COG0843    46 GPGLGLLSPETYNQLFTMHGTIMIFFFATP-FLAGFGNYLVPLQIGARDMAFPRLNALSFW 105

Ubiquinol oxidase subunit I. Ubiquinol oxidase, the terminal oxidase in the respiratory chains of aerobic bacteria, is a multi-chain transmembrane protein located in the cell membrane. It catalyzes the reduction of O2 and simultaneously pumps protons across the membrane. The number of subunits in ubiquinol oxidase varies from two to five. Subunit I contains a heme-copper binuclear center (the active site where O2 is reduced to water) formed by a high-spin heme and a copper ion. It also contains a low-spin heme, believed to participate in the transfer of electrons from ubiquinol to the binuclear center. For every reduction of an O2 molecule, eight protons are taken from the inside aqueous compartment and four electrons are taken from ubiquinol on the opposite side of the membrane. The four electrons and four of the protons are used in the reduction of O2; the four remaining protons are pumped across the membrane. This charge separation of four charges contributes to the electrochemical gradient used for ATP synthesis. Two proton channels, the D-pathway and K-pathway, leading to the binuclear center have been identified in subunit I. It is generally believed that the channels contain water molecules that act as 'proton wires' to transfer the protons. A well-defined pathway for the transfer of pumped protons beyond the binuclear center has not been identified. Electrons are believed to be transferred directly from ubiquinol (the electron donor) to the low-spin heme, and directly from the low-spin heme to the binuclear center.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|
gi 2087301634   3 PGSMLGDDQLYNVAVTAHGLIMIFFFVMPVLLGgFGNWLVPLYIGAPDMAFPRLNNISFW 62
Cdd:cd01662    39 PGNDFLSPEHYNQIFTMHGTIMIFLFAMPLVFG-LMNYLVPLQIGARDVAFPRLNALSFW 97

cytochrome o ubiquinol oxidase subunit I; Provisional

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|
gi 2087301634  13 YNVAVTAHGLIMIFFFVMPVLLGgFGNWLVPLYIGAPDMAFPRLNNISFW 62
Cdd:PRK15017   99 YDQIFTAHGVIMIFFVAMPFVIG-LMNLVVPLQIGARDVAFPFLNNLSFW 147