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
                  ....*....|....*....|....*....|....*....|....*.
gi 1510288570   1 YPPLAGNLAHAGASVDLAIFSLHLAGVSSILGAINFITTAINMKPP 46
Cdd:cd01663   120 YPPLSSILAHSGPSVDLAIFSLHLAGISSILGAINFITTIFNMRAP 165

Cytochrome C and Quinol oxidase polypeptide I; Cytochrome c oxidase (E.C:7.1.1.9) is a key enzyme in aerobic metabolism. Proton pumping haem-copper oxidases represent the terminal, energy-transfer enzymes of respiratory chains in prokaryotes and eukaryotes. The CuB-haem a3 (or haem o) binuclear centre, associated with the largest subunit I of cytochrome c and ubiquinol oxidases (E.C:1.10.3.11), is directly involved in the coupling between dioxygen reduction and proton pumping. Some terminal oxidases generate a transmembrane proton gradient across the plasma membrane (prokaryotes) or the mitochondrial inner membrane (eukaryotes). The enzyme complex consists of 3-4 subunits (prokaryotes) up to 13 polypeptides (mammals) of which only the catalytic subunit (equivalent to mammalian subunit I (COXI) is found in all haem-copper respiratory oxidases. The presence of a bimetallic centre (formed by a high-spin haem and copper B) as well as a low-spin haem, both ligated to six conserved histidine residues near the outer side of four transmembrane spans within CO I is common to all family members.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*.
gi 1510288570   1 YPPLAGnlahagasVDLAIFSLHLAGVSSILGAINFITTAINMKPP 46
Cdd:pfam00115 112 YPPLVG--------VDLWYIGLLLAGVSSLLGAINFIVTILKRRAP 149

cytochrome c oxidase subunit I; Provisional

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*.
gi 1510288570   1 YPPLAGNLAHAGASVDLAIFSLHLAGVSSILGAINFITTAINMKPP 46
Cdd:MTH00153  127 YPPLSSNIAHSGASVDLAIFSLHLAGISSILGAINFITTIINMRSK 172

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
                  ....*....|....*....|....*....|....*....|....*.
gi 1510288570   1 YPPLAGNLAHAGASVDLAIFSLHLAGVSSILGAINFITTAINMKPP 46
Cdd:cd01663   120 YPPLSSILAHSGPSVDLAIFSLHLAGISSILGAINFITTIFNMRAP 165

cytochrome c oxidase subunit I; Provisional

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*.
gi 1510288570   1 YPPLAGNLAHAGASVDLAIFSLHLAGVSSILGAINFITTAINMKPP 46
Cdd:MTH00183  129 YPPLAGNLAHAGASVDLTIFSLHLAGVSSILGAINFITTIINMKPP 174

cytochrome c oxidase subunit I; Provisional

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*.
gi 1510288570   1 YPPLAGNLAHAGASVDLAIFSLHLAGVSSILGAINFITTAINMKPP 46
Cdd:MTH00223  126 YPPLSSNLAHAGPSVDLAIFSLHLAGVSSILGAINFITTIINMRSP 171

cytochrome c oxidase subunit I; Provisional

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*.
gi 1510288570   1 YPPLAGNLAHAGASVDLAIFSLHLAGVSSILGAINFITTAINMKPP 46
Cdd:MTH00037  129 YPPLSSNIAHAGGSVDLAIFSLHLAGASSILASINFITTIINMRTP 174

cytochrome c oxidase subunit I; Provisional

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*.
gi 1510288570   1 YPPLAGNLAHAGASVDLAIFSLHLAGVSSILGAINFITTAINMKPP 46
Cdd:MTH00184  131 YPPLSSIQAHSGGSVDMAIFSLHLAGISSILGAMNFITTIFNMRAP 176

cytochrome c oxidase subunit I; Provisional

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*
gi 1510288570   1 YPPLAgNLAHAGASVDLAIFSLHLAGVSSILGAINFITTAINMKP 45
Cdd:MTH00079  130 YPPLS-TLGHPGSSVDLAIFSLHCAGISSILGGINFMVTTKNLRS 173

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

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*.
gi 1510288570   1 YPPLAGNLAHAGASVDLAIFSLHLAGVSSILGAINFITTAINMKPP 46
Cdd:COG0843   131 YPPLSGLEASPGVGVDLWLLGLALFGVGSILGGVNFIVTILKMRAP 176

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
                  ....*....|....*....|....*....|....*....|....*.
gi 1510288570   1 YPPLAGNLAHAGASVDLAIFSLHLAGVSSILGAINFITTAINMKPP 46
Cdd:cd01662   123 YPPLSGLEYSPGVGVDYWILGLQFSGIGTLLGAINFIVTILKMRAP 168

Cytochrome C and Quinol oxidase polypeptide I; Cytochrome c oxidase (E.C:7.1.1.9) is a key enzyme in aerobic metabolism. Proton pumping haem-copper oxidases represent the terminal, energy-transfer enzymes of respiratory chains in prokaryotes and eukaryotes. The CuB-haem a3 (or haem o) binuclear centre, associated with the largest subunit I of cytochrome c and ubiquinol oxidases (E.C:1.10.3.11), is directly involved in the coupling between dioxygen reduction and proton pumping. Some terminal oxidases generate a transmembrane proton gradient across the plasma membrane (prokaryotes) or the mitochondrial inner membrane (eukaryotes). The enzyme complex consists of 3-4 subunits (prokaryotes) up to 13 polypeptides (mammals) of which only the catalytic subunit (equivalent to mammalian subunit I (COXI) is found in all haem-copper respiratory oxidases. The presence of a bimetallic centre (formed by a high-spin haem and copper B) as well as a low-spin haem, both ligated to six conserved histidine residues near the outer side of four transmembrane spans within CO I is common to all family members.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*.
gi 1510288570   1 YPPLAGnlahagasVDLAIFSLHLAGVSSILGAINFITTAINMKPP 46
Cdd:pfam00115 112 YPPLVG--------VDLWYIGLLLAGVSSLLGAINFIVTILKRRAP 149