ID   COX3_CYACA              Reviewed;         270 AA.
AC   P48873;
DT   01-FEB-1996, integrated into UniProtKB/Swiss-Prot.
DT   01-FEB-1996, sequence version 1.
DT   25-MAY-2022, entry version 94.
DE   RecName: Full=Cytochrome c oxidase subunit 3;
DE            EC=7.1.1.9;
DE   AltName: Full=Cytochrome c oxidase polypeptide III;
GN   Name=COX3; Synonyms=COXIII;
OS   Cyanidium caldarium (Red alga).
OG   Mitochondrion.
OC   Eukaryota; Rhodophyta; Bangiophyceae; Cyanidiales; Cyanidiaceae; Cyanidium.
OX   NCBI_TaxID=2771;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RC   STRAIN=RK-1;
RA   Viehmann S.;
RL   Thesis (1995), Justus Liebig University / Frankfurt, Germany.
CC   -!- FUNCTION: Component of the cytochrome c oxidase, the last enzyme in the
CC       mitochondrial electron transport chain which drives oxidative
CC       phosphorylation. The respiratory chain contains 3 multisubunit
CC       complexes succinate dehydrogenase (complex II, CII), ubiquinol-
CC       cytochrome c oxidoreductase (cytochrome b-c1 complex, complex III,
CC       CIII) and cytochrome c oxidase (complex IV, CIV), that cooperate to
CC       transfer electrons derived from NADH and succinate to molecular oxygen,
CC       creating an electrochemical gradient over the inner membrane that
CC       drives transmembrane transport and the ATP synthase. Cytochrome c
CC       oxidase is the component of the respiratory chain that catalyzes the
CC       reduction of oxygen to water. Electrons originating from reduced
CC       cytochrome c in the intermembrane space (IMS) are transferred via the
CC       dinuclear copper A center (CU(A)) of subunit 2 and heme A of subunit 1
CC       to the active site in subunit 1, a binuclear center (BNC) formed by
CC       heme A3 and copper B (CU(B)). The BNC reduces molecular oxygen to 2
CC       water molecules using 4 electrons from cytochrome c in the IMS and 4
CC       protons from the mitochondrial matrix. {ECO:0000250|UniProtKB:P00420}.
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=4 Fe(II)-[cytochrome c] + 8 H(+)(in) + O2 = 4 Fe(III)-
CC         [cytochrome c] + 4 H(+)(out) + 2 H2O; Xref=Rhea:RHEA:11436,
CC         Rhea:RHEA-COMP:10350, Rhea:RHEA-COMP:14399, ChEBI:CHEBI:15377,
CC         ChEBI:CHEBI:15378, ChEBI:CHEBI:15379, ChEBI:CHEBI:29033,
CC         ChEBI:CHEBI:29034; EC=7.1.1.9;
CC         Evidence={ECO:0000250|UniProtKB:P00420};
CC       PhysiologicalDirection=left-to-right; Xref=Rhea:RHEA:11437;
CC         Evidence={ECO:0000250|UniProtKB:P00420};
CC   -!- SUBUNIT: Component of the cytochrome c oxidase (complex IV, CIV), a
CC       multisubunit enzyme composed of a catalytic core of 3 subunits and
CC       several supernumerary subunits. The complex exists as a monomer or a
CC       dimer and forms supercomplexes (SCs) in the inner mitochondrial
CC       membrane with ubiquinol-cytochrome c oxidoreductase (cytochrome b-c1
CC       complex, complex III, CIII). {ECO:0000250|UniProtKB:P00420}.
CC   -!- SUBCELLULAR LOCATION: Mitochondrion inner membrane
CC       {ECO:0000250|UniProtKB:P00420}; Multi-pass membrane protein
CC       {ECO:0000250|UniProtKB:P00420}.
CC   -!- SIMILARITY: Belongs to the cytochrome c oxidase subunit 3 family.
CC       {ECO:0000305}.
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DR   EMBL; Z48930; CAA88770.1; -; Genomic_DNA.
DR   PIR; S62760; S62760.
DR   AlphaFoldDB; P48873; -.
DR   SMR; P48873; -.
DR   GO; GO:0016021; C:integral component of membrane; IEA:UniProtKB-KW.
DR   GO; GO:0005743; C:mitochondrial inner membrane; IEA:UniProtKB-SubCell.
DR   GO; GO:0004129; F:cytochrome-c oxidase activity; IEA:UniProtKB-EC.
DR   GO; GO:0019646; P:aerobic electron transport chain; IEA:InterPro.
DR   CDD; cd01665; Cyt_c_Oxidase_III; 1.
DR   Gene3D; 1.20.120.80; -; 1.
DR   InterPro; IPR024791; Cyt_c/ubiquinol_Oxase_su3.
DR   InterPro; IPR033945; Cyt_c_oxase_su3_dom.
DR   InterPro; IPR000298; Cyt_c_oxidase-like_su3.
DR   InterPro; IPR035973; Cyt_c_oxidase_su3-like_sf.
DR   InterPro; IPR013833; Cyt_c_oxidase_su3_a-hlx.
DR   PANTHER; PTHR11403; PTHR11403; 1.
DR   Pfam; PF00510; COX3; 1.
DR   SUPFAM; SSF81452; SSF81452; 1.
DR   PROSITE; PS50253; COX3; 1.
PE   3: Inferred from homology;
KW   Membrane; Mitochondrion; Mitochondrion inner membrane; Translocase;
KW   Transmembrane; Transmembrane helix.
FT   CHAIN           1..270
FT                   /note="Cytochrome c oxidase subunit 3"
FT                   /id="PRO_0000183761"
FT   TRANSMEM        21..41
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        46..66
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        90..110
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        131..151
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        167..187
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        205..225
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        248..268
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
SQ   SEQUENCE   270 AA;  31564 MW;  52917FBDCAE953C5 CRC64;
     MMSLIVKDLQ RYPFHLVDPS PWPFVASFSA LIILLGGVLY FHTYQGSLVI LFFGIFFLLL
     IIFVWWRDVV RESTFEGNHT TMVQLGMRYG IMLFIFSEVI LFIAFFWAFF HNSLIPALET
     GVVWPPKGIQ FFSPWDIPFL NTIILLLSGC AVTWSHNCII SGFRRQAIFS LILTIGLALI
     FTIFQIYEYA IASFHLSDGA YGSTFFMITG LHGFHVIVGT FFLFVCMFRL VQYHFTMQHH
     YGFEAATWYW HFVDVVWLFL FVSIYWWGSF