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 411167620   1 PSLIILIFSMIFSSGPGTGWTIYPPLSNSLFNSGISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMNKISLFSW 80
Cdd:cd01663   98 PSLLLLLLSALVEGGAGTGWTVYPPLSSILAHSGPSVDLAIFSLHLAGISSILGAINFITTIFNMRAPGMTLEKMPLFVW 177

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 411167620  81 SILLTSILLLLSLPVLAGAITMLLFDRNMNTSFFDPSGGGDP 122
Cdd:cd01663  178 SVLITAFLLLLSLPVLAGAITMLLTDRNFNTSFFDPAGGGDP 219

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 411167620   1 PSLIILIFSMIFSSGPGTGWTIYPPLSNSLFNSGISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMNKISLFSW 80
Cdd:cd01663   98 PSLLLLLLSALVEGGAGTGWTVYPPLSSILAHSGPSVDLAIFSLHLAGISSILGAINFITTIFNMRAPGMTLEKMPLFVW 177

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 411167620  81 SILLTSILLLLSLPVLAGAITMLLFDRNMNTSFFDPSGGGDP 122
Cdd:cd01663  178 SVLITAFLLLLSLPVLAGAITMLLTDRNFNTSFFDPAGGGDP 219

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

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 411167620   4 IILIFSMIFSSGPGTGWTIYPPLSNSLFNSGISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMNKISLFSWSIL 83
Cdd:COG0843  112 LLLLISLFVGGAADVGWTFYPPLSGLEASPGVGVDLWLLGLALFGVGSILGGVNFIVTILKMRAPGMTLMRMPLFTWAAL 191

                         90       100       110
                 ....*....|....*....|....*....|....*....
gi 411167620  84 LTSILLLLSLPVLAGAITMLLFDRNMNTSFFDPSGGGDP 122
Cdd:COG0843  192 VTSILILLAFPVLAAALLLLLLDRSLGTHFFDPAGGGDP 230

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 411167620   1 PSLIILIFSMIFSSGPGTGWTIYPPLSNSLFNSGISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMNKISLFSW 80
Cdd:cd01663   98 PSLLLLLLSALVEGGAGTGWTVYPPLSSILAHSGPSVDLAIFSLHLAGISSILGAINFITTIFNMRAPGMTLEKMPLFVW 177

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 411167620  81 SILLTSILLLLSLPVLAGAITMLLFDRNMNTSFFDPSGGGDP 122
Cdd:cd01663  178 SVLITAFLLLLSLPVLAGAITMLLTDRNFNTSFFDPAGGGDP 219

cytochrome c oxidase subunit I; Provisional

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 411167620   1 PSLIILIFSMIFSSGPGTGWTIYPPLSNSLFNSGISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMNKISLFSW 80
Cdd:MTH00223 104 PSLYLLLSSSAVESGVGTGWTVYPPLSSNLAHAGPSVDLAIFSLHLAGVSSILGAINFITTIINMRSPGMQLERLPLFVW 183

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 411167620  81 SILLTSILLLLSLPVLAGAITMLLFDRNMNTSFFDPSGGGDP 122
Cdd:MTH00223 184 SVKVTAFLLLLSLPVLAGAITMLLTDRNFNTSFFDPAGGGDP 225

cytochrome c oxidase subunit I; Provisional

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 411167620   1 PSLIILIFSMIFSSGPGTGWTIYPPLSNSLFNSGISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMNKISLFSW 80
Cdd:MTH00116 107 PSFLLLLASSTVEAGAGTGWTVYPPLAGNLAHAGASVDLAIFSLHLAGVSSILGAINFITTCINMKPPAMSQYQTPLFVW 186

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 411167620  81 SILLTSILLLLSLPVLAGAITMLLFDRNMNTSFFDPSGGGDP 122
Cdd:MTH00116 187 SVLITAVLLLLSLPVLAAGITMLLTDRNLNTTFFDPAGGGDP 228

cytochrome c oxidase subunit I; Validated

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 411167620   1 PSLIILIFSMIFSSGPGTGWTIYPPLSNSLFNSGISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMNKISLFSW 80
Cdd:MTH00007 104 PALILLVSSAAVEKGVGTGWTVYPPLASNLAHAGPSVDLAIFSLHLAGVSSILGAINFITTVINMRWKGLRLERIPLFVW 183

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 411167620  81 SILLTSILLLLSLPVLAGAITMLLFDRNMNTSFFDPSGGGDP 122
Cdd:MTH00007 184 AVVITVVLLLLSLPVLAGAITMLLTDRNLNTSFFDPAGGGDP 225

cytochrome c oxidase subunit I; Provisional

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 411167620   1 PSLIILIFSMIFSSGPGTGWTIYPPLSNSLFNSGISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMNKISLFSW 80
Cdd:MTH00182 109 PALILLLGSAFVEQGAGTGWTVYPPLSSIQAHSGGAVDMAIFSLHLAGVSSILGAINFITTIFNMRAPGVTFNRLPLFVW 188

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 411167620  81 SILLTSILLLLSLPVLAGAITMLLFDRNMNTSFFDPSGGGDP 122
Cdd:MTH00182 189 SILITAFLLLLSLPVLAGAITMLLTDRNFNTTFFDPAGGGDP 230

cytochrome c oxidase subunit I; Provisional

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 411167620   1 PSLIILIFSMIFSSGPGTGWTIYPPLSNSLFNSGISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMNKISLFSW 80
Cdd:MTH00184 109 PALTLLLGSAFVEQGAGTGWTVYPPLSSIQAHSGGSVDMAIFSLHLAGISSILGAMNFITTIFNMRAPGITMDRMPLFVW 188

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 411167620  81 SILLTSILLLLSLPVLAGAITMLLFDRNMNTSFFDPSGGGDP 122
Cdd:MTH00184 189 SILVTTFLLLLSLPVLAGAITMLLTDRNFNTTFFDPAGGGDP 230

cytochrome c oxidase subunit I; Validated

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 411167620   1 PSLIILIFSMIFSSGPGTGWTIYPPLSNSLFNSGISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMNKISLFSW 80
Cdd:MTH00103 107 PSFLLLLASSMVEAGAGTGWTVYPPLAGNLAHAGASVDLTIFSLHLAGVSSILGAINFITTIINMKPPAMSQYQTPLFVW 186

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 411167620  81 SILLTSILLLLSLPVLAGAITMLLFDRNMNTSFFDPSGGGDP 122
Cdd:MTH00103 187 SVLITAVLLLLSLPVLAAGITMLLTDRNLNTTFFDPAGGGDP 228

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 411167620   1 PSLIILIFSMIFSSGPGTGWTIYPPLSNSLFNSGISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMNKISLFSW 80
Cdd:cd00919   95 PGLLLLLSSVLVGGGAGTGWTFYPPLSTLSYSSGVGVDLAILGLHLAGVSSILGAINFITTILNMRAPGMTLDKMPLFVW 174

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 411167620  81 SILLTSILLLLSLPVLAGAITMLLFDRNMNTSFFDPSGGGDP 122
Cdd:cd00919  175 SVLVTAILLLLALPVLAAALVMLLLDRNFGTSFFDPAGGGDP 216

cytochrome c oxidase subunit I; Provisional

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 411167620   1 PSLIILIFSMIFSSGPGTGWTIYPPLSNSLFNSGISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMNKISLFSW 80
Cdd:MTH00026 108 PALFLLLGSSLVEQGAGTGWTVYPPLASIQAHSGGSVDMAIFSLHLAGLSSILGAMNFITTVMNMRTPGMTMSRIPLFVW 187

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|..
gi 411167620  81 SILLTSILLLLSLPVLAGAITMLLFDRNMNTSFFDPSGGGDP 122
Cdd:MTH00026 188 SVFITAILLLLSLPVLAGAITMLLTDRNFNTTFFDPAGGGDP 229

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        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 411167620   4 IILIFSMIFSSGPGTGWTIYPPLSNSLFNSGISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMNKISLFSWSIL 83
Cdd:cd01662  104 LLLNASLLIGGFPDAGWFAYPPLSGLEYSPGVGVDYWILGLQFSGIGTLLGAINFIVTILKMRAPGMTLMRMPIFTWTTL 183

                         90       100       110
                 ....*....|....*....|....*....|....*....
gi 411167620  84 LTSILLLLSLPVLAGAITMLLFDRNMNTSFFDPSGGGDP 122
Cdd:cd01662  184 VTSILILFAFPVLTAALALLELDRYFGTHFFTNALGGNP 222

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        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 411167620    1 PSLIILIFSMifsSGPGTGWTIYPPLsnslfnsgISVDLMIFSLHMAGVSSIMGSINMISTIINIRSKLMLMnKISLFSW 80
Cdd:pfam00115  93 LGAVLLLASF---GGATTGWTEYPPL--------VGVDLWYIGLLLAGVSSLLGAINFIVTILKRRAPGMTL-RMPLFVW 160

                          90       100       110
                  ....*....|....*....|....*....|....*.
gi 411167620   81 SILLTSILLLLSLPVLAGAITMLLFDRNMNTSFFDP 116
Cdd:pfam00115 161 AILATAILILLAFPVLAAALLLLLLDRSLGAGGGDP 196