ID   COX42_THUOB             Reviewed;         176 AA.
AC   P80971; Q9I8T9;
DT   01-NOV-1997, integrated into UniProtKB/Swiss-Prot.
DT   03-APR-2002, sequence version 2.
DT   02-SEP-2026, entry version 95.
DE   RecName: Full=Cytochrome c oxidase subunit 4 isoform 2, mitochondrial;
DE   AltName: Full=Cytochrome c oxidase subunit IV isoform 2;
DE            Short=COX IV-2;
DE   Flags: Precursor;
OS   Thunnus obesus (Bigeye tuna).
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
OC   Actinopterygii; Neopterygii; Teleostei; Neoteleostei; Acanthomorphata;
OC   Pelagiaria; Scombriformes; Scombridae; Thunnus.
OX   NCBI_TaxID=8241;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA].
RC   TISSUE=Heart, Liver, and Muscle;
RX   PubMed=11004496; DOI=10.1016/s0167-4781(00)00083-x;
RA   Huettemann M.;
RT   "New isoforms of cytochrome c oxidase subunit IV in tuna fish.";
RL   Biochim. Biophys. Acta 1492:242-246(2000).
RN   [2]
RP   PROTEIN SEQUENCE OF 29-38.
RC   TISSUE=Heart, and Liver;
RX   PubMed=9310366; DOI=10.1111/j.1432-1033.1997.t01-1-00099.x;
RA   Arnold S., Lee I., Kim M., Song E., Linder D., Lottspeich F., Kadenbach B.;
RT   "The subunit structure of cytochrome-c oxidase from tuna heart and liver.";
RL   Eur. J. Biochem. 248:99-103(1997).
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:P00424}.
CC   -!- PATHWAY: Energy metabolism; oxidative phosphorylation.
CC       {ECO:0000250|UniProtKB:P00424}.
CC   -!- SUBUNIT: Component of the cytochrome c oxidase (complex IV, CIV), a
CC       multisubunit enzyme composed of 14 subunits. The complex is composed of
CC       a catalytic core of 3 subunits MT-CO1, MT-CO2 and MT-CO3, encoded in
CC       the mitochondrial DNA, and 11 supernumerary subunits COX4I, COX5A,
CC       COX5B, COX6A, COX6B, COX6C, COX7A, COX7B, COX7C, COX8 and COXFA4, which
CC       are encoded in the nuclear genome. The complex exists as a monomer or a
CC       dimer and forms supercomplexes (SCs) in the inner mitochondrial
CC       membrane with NADH-ubiquinone oxidoreductase (complex I, CI) and
CC       ubiquinol-cytochrome c oxidoreductase (cytochrome b-c1 complex, complex
CC       III, CIII), resulting in different assemblies (supercomplex
CC       SCI(1)III(2)IV(1) and megacomplex MCI(2)III(2)IV(2)).
CC       {ECO:0000250|UniProtKB:P00423}.
CC   -!- SUBCELLULAR LOCATION: Mitochondrion inner membrane
CC       {ECO:0000250|UniProtKB:P00423}; Single-pass membrane protein
CC       {ECO:0000250|UniProtKB:P00423}.
CC   -!- SIMILARITY: Belongs to the cytochrome c oxidase IV family.
CC       {ECO:0000305}.
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DR   EMBL; AF204871; AAF79934.1; -; mRNA.
DR   PIR; S77980; S77980.
DR   AlphaFoldDB; P80971; -.
DR   SMR; P80971; -.
DR   UniPathway; UPA00705; -.
DR   GO; GO:0005743; C:mitochondrial inner membrane; ISS:UniProtKB.
DR   GO; GO:0045277; C:respiratory chain complex IV; IEA:InterPro.
DR   GO; GO:0006123; P:mitochondrial electron transport, cytochrome c to oxygen; IEA:InterPro.
DR   CDD; cd00922; Cyt_c_Oxidase_IV; 1.
DR   FunFam; 1.10.442.10:FF:000001; Cytochrome c oxidase subunit 4 isoform 1; 1.
DR   Gene3D; 1.10.442.10; Cytochrome c oxidase subunit IV; 1.
DR   InterPro; IPR013288; Cyt_c_oxidase_su4.
DR   InterPro; IPR004203; Cyt_c_oxidase_su4_fam.
DR   InterPro; IPR036639; Cyt_c_oxidase_su4_sf.
DR   PANTHER; PTHR10707:SF15; CYTOCHROME C OXIDASE SUBUNIT 4; 1.
DR   PANTHER; PTHR10707; CYTOCHROME C OXIDASE SUBUNIT IV; 1.
DR   Pfam; PF02936; COX4; 1.
DR   PRINTS; PR01873; CYTCOXIDASE4.
DR   SUPFAM; SSF81406; Mitochondrial cytochrome c oxidase subunit IV; 1.
PE   1: Evidence at protein level;
KW   Direct protein sequencing; Membrane; Mitochondrion;
KW   Mitochondrion inner membrane; Transit peptide; Transmembrane;
KW   Transmembrane helix.
FT   TRANSIT         1..28
FT                   /note="Mitochondrion"
FT                   /evidence="ECO:0000269|PubMed:9310366"
FT   CHAIN           29..176
FT                   /note="Cytochrome c oxidase subunit 4 isoform 2,
FT                   mitochondrial"
FT                   /id="PRO_0000006093"
FT   TOPO_DOM        29..106
FT                   /note="Mitochondrial matrix"
FT                   /evidence="ECO:0000250|UniProtKB:P00423"
FT   TRANSMEM        107..132
FT                   /note="Helical"
FT                   /evidence="ECO:0000250|UniProtKB:P00423"
FT   TOPO_DOM        133..176
FT                   /note="Mitochondrial intermembrane"
FT                   /evidence="ECO:0000250|UniProtKB:P00423"
FT   CONFLICT        33
FT                   /note="L -> H (in Ref. 2; AA sequence)"
FT                   /evidence="ECO:0000305"
SQ   SEQUENCE   176 AA;  20470 MW;  4EEB4EF17BC58AD4 CRC64;
     MLRLTAGRVR SLLAGRATAA FSTSSARMAS HDLEVAESVD MSKPLYWDRL DTPLPDRPYK
     EDLTAADKSL KQKEKGPWGQ LSKEEKIALY RLMFCQTYSE MKQPSSEWKT VFGGIFIFLG
     FTGLVVWWQA LYVYPPRPRT FDDEWKAKQL KRMLDMRVNP IEGFSAKWDY EKGQWK
//