ID   COX3_HELAN              Reviewed;         265 AA.
AC   P32808;
DT   01-OCT-1993, integrated into UniProtKB/Swiss-Prot.
DT   01-OCT-1993, sequence version 1.
DT   22-FEB-2023, entry version 98.
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   Helianthus annuus (Common sunflower).
OG   Mitochondrion.
OC   Eukaryota; Viridiplantae; Streptophyta; Embryophyta; Tracheophyta;
OC   Spermatophyta; Magnoliopsida; eudicotyledons; Gunneridae; Pentapetalae;
OC   asterids; campanulids; Asterales; Asteraceae; Asteroideae;
OC   Heliantheae alliance; Heliantheae; Helianthus.
OX   NCBI_TaxID=4232;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RC   STRAIN=cv. Gloriasol;
RX   PubMed=2174745; DOI=10.1007/bf00318217;
RA   Quagliariello C., Saiardi A., Gallerani R.;
RT   "The cytochrome oxidase subunit III gene in sunflower mitochondria is
RT   cotranscribed with an open reading frame conserved in higher plants.";
RL   Curr. Genet. 18:355-363(1990).
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; X57669; CAA40865.1; -; Genomic_DNA.
DR   PIR; S14123; S14123.
DR   AlphaFoldDB; P32808; -.
DR   SMR; P32808; -.
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; 1.10.287.70; -; 1.
DR   Gene3D; 1.20.120.80; Cytochrome c oxidase, subunit III, four-helix bundle; 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:SF7; CYTOCHROME C OXIDASE SUBUNIT 3; 1.
DR   PANTHER; PTHR11403; CYTOCHROME C OXIDASE SUBUNIT III; 1.
DR   Pfam; PF00510; COX3; 1.
DR   SUPFAM; SSF81452; Cytochrome c oxidase subunit III-like; 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..265
FT                   /note="Cytochrome c oxidase subunit 3"
FT                   /id="PRO_0000183790"
FT   TRANSMEM        16..36
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        41..61
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        81..101
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        162..182
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        200..220
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        245..265
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
SQ   SEQUENCE   265 AA;  29423 MW;  BE30F0236E86C9EE CRC64;
     MIESQRHSYH LVDPSPWPIS GSLGALATTV GGVMYMHSFQ GGATLLSLGL IFILYTMFVW
     WRDVLRESTL EGHHTKVVQL GPRYGFILFI VSEVMFLFAL FRASSHSSLA PTVEIGGIWP
     PKGIAVLDPR EIPFLNTPIP LSSGAAVTWA HHAILAGKEK RAVYALVATV SLALVFTAFQ
     GMEYYQAPST ISDSIYGSTF FLATGFHGFH VIIGTLFSIV CGIRQYLGHL TKEHHVGFEA
     AAWYWHFVDV VRLFPFVSIY WWGGI
//