COX5B explained

Cytochrome c oxidase subunit 5B, mitochondrial is an enzyme in humans that is a subunit of the cytochrome c oxidase complex, also known as Complex IV, the last enzyme in the mitochondrial electron transport chain.^[1] In humans, cytochrome c oxidase subunit 5B is encoded by the COX5B gene.

Structure

The enzyme weighs 14 kDa and is composed of 129 amino acids.^[2] The protein is a subunit of Complex IV, which consists of 13 mitochondrial- and nuclear-encoded subunits. The sequence of subunit Vb is well conserved and includes three conserved cysteines that coordinate the zinc ion.^{[3] [4]} Two of these cysteines are clustered in the C-terminal section of the subunit.

Gene

The COX5B gene, located on the q arm of chromosome 2 in position 11.2, is made up of 4 exons and is 2,137 base pairs in length.^[1]

Function

Cytochrome c oxidase (COX) is the terminal enzyme of the mitochondrial respiratory chain. It is a multi-subunit enzyme complex that couples the transfer of electrons from cytochrome c to oxygen and contributes to a proton electrochemical gradient across the inner mitochondrial membrane to drive ATP synthesis via protonmotive force. The mitochondrially-encoded subunits perform the electron transfer of proton pumping activities. The functions of the nuclear-encoded subunits are unknown but they may play a role in the regulation and assembly of the complex.

Summary reaction:

4 Fe²⁺-cytochrome c + 8 H⁺_in + O₂ → 4 Fe³⁺-cytochrome c + 2 H₂O + 4 H⁺_out^[5]

Clinical significance

COX5A and COX5B are involved in the regulation of cancer cell metabolism by Bcl-2.^[6]

The Trans-activator of transcription protein (Tat) of human immunodeficiency virus (HIV) inhibits cytochrome c oxidase (COX) activity in permeabilized mitochondria isolated from both mouse and human liver, heart, and brain samples.^[7]

Interactions

COX5B has been shown to interact with Androgen receptor.^[8]

Further reading

• Lomax MI, Hsieh CL, Darras BT, Francke U . Structure of the human cytochrome c oxidase subunit Vb gene and chromosomal mapping of the coding gene and of seven pseudogenes . Genomics . 10 . 1 . 1–9 . 1991 . 1646156 . 10.1016/0888-7543(91)90476-U . 2027.42/29338 . free .
• Romero N, Marsac C, Fardeau M, Droste M, Schneyder B, Kadenbach B . Immunohistochemical demonstration of fibre type-specific isozymes of cytochrome c oxidase in human skeletal muscle . Histochemistry . 94 . 2 . 211–5 . 1990 . 2162812 . 10.1007/BF02440190 . 33365867 .
• Zeviani M, Sakoda S, Sherbany AA, Nakase H, Rizzuto R, Samitt CE, DiMauro S, Schon EA . Sequence of cDNAs encoding subunit Vb of human and bovine cytochrome c oxidase . Gene . 65 . 1 . 1–11 . 1988 . 2840351 . 10.1016/0378-1119(88)90411-8 .
• Hughes GJ, Frutiger S, Paquet N, Pasquali C, Sanchez JC, Tissot JD, Bairoch A, Appel RD, Hochstrasser DF . Human liver protein map: update 1993 . Electrophoresis . 14 . 11 . 1216–22 . 1993 . 8313870 . 10.1002/elps.11501401181 . 33424554 .
• Bachman NJ, Yang TL, Dasen JS, Ernst RE, Lomax MI . Phylogenetic footprinting of the human cytochrome c oxidase subunit VB promoter . Arch. Biochem. Biophys. . 333 . 1 . 152–62 . 1996 . 8806766 . 10.1006/abbi.1996.0376 .
• Lefai E, Vincent A, Boespflug-Tanguy O, Tanguy A, Alziari S . Quantitative decrease of human cytochrome c oxidase during development: evidences for a post-transcriptional regulation . Biochim. Biophys. Acta . 1318 . 1–2 . 191–201 . 1997 . 9030264 . 10.1016/S0005-2728(96)00136-3 .
• Wu H, Rao GN, Dai B, Singh P . Autocrine gastrins in colon cancer cells Up-regulate cytochrome c oxidase Vb and down-regulate efflux of cytochrome c and activation of caspase-3 . J. Biol. Chem. . 275 . 42 . 32491–8 . 2000 . 10915781 . 10.1074/jbc.M002458200 . free .
• Beauchemin AM, Gottlieb B, Beitel LK, Elhaji YA, Pinsky L, Trifiro MA . Cytochrome c oxidase subunit Vb interacts with human androgen receptor: a potential mechanism for neurotoxicity in spinobulbar muscular atrophy . Brain Res. Bull. . 56 . 3–4 . 285–97 . 2002 . 11719263 . 10.1016/S0361-9230(01)00583-4 . 24740136 .
• Ewing RM, Chu P, Elisma F, Li H, Taylor P, Climie S, McBroom-Cerajewski L, Robinson MD, O'Connor L, Li M, Taylor R, Dharsee M, Ho Y, Heilbut A, Moore L, Zhang S, Ornatsky O, Bukhman YV, Ethier M, Sheng Y, Vasilescu J, Abu-Farha M, Lambert JP, Duewel HS, Stewart II, Kuehl B, Hogue K, Colwill K, Gladwish K, Muskat B, Kinach R, Adams SL, Moran MF, Morin GB, Topaloglou T, Figeys D . Large-scale mapping of human protein-protein interactions by mass spectrometry . Mol. Syst. Biol. . 3 . 1 . 89 . 2007 . 17353931 . 1847948 . 10.1038/msb4100134 .

External links

• • Mass spectrometry characterization of COX5B at COPaKB
• Cytochrome c oxidase subunit Vb in PROSITE

Notes and References

1. Web site: Entrez Gene: COX5B cytochrome c oxidase subunit Vb.
2. Web site: Cytochrome c oxidase subunit 5B, mitochondrial . Cardiac Organellar Protein Atlas Knowledgebase (COPaKB) . 2018-07-18 . https://web.archive.org/web/20180719024525/https://amino.heartproteome.org/web/protein/P10606 . 2018-07-19 . dead .
3. Rizzuto R, Sandona D, Brini M, Capaldi RA, Bisson R . The most conserved nuclear-encoded polypeptide of cytochrome c oxidase is the putative zinc-binding subunit: primary structure of subunit V from the slime mold Dictyostelium discoideum . Biochim. Biophys. Acta . 1129 . 1 . 100–104 . 1991 . 1661610 . 10.1016/0167-4781(91)90220-G.
4. Tsukihara T, Yamaguchi H, Aoyama H, Yamashita E, Tomizaki T, Shinzawa-Itoh K, Nakashima R, Yaono R, Yoshikawa S . The whole structure of the 13-subunit oxidized cytochrome c oxidase at 2.8 A . Science . 272 . 5265 . 1136–1144 . 1996 . 8638158 . 10.1126/science.272.5265.1136 . 1996Sci...272.1136T. 20860573 .
5. Book: Pratt. Donald Voet, Judith G. Voet, Charlotte W.. Fundamentals of biochemistry : life at the molecular level. 2013. Wiley. Hoboken, NJ. 978-0-470-54784-7. 18 . 581–620. 4th.
6. Chen ZX, Pervaiz S . Involvement of cytochrome c oxidase subunits Va and Vb in the regulation of cancer cell metabolism by Bcl-2 . Cell Death and Differentiation . 17 . 3 . 408–20 . Mar 2010 . 19834492 . 10.1038/cdd.2009.132 . free .
7. Lecoeur H, Borgne-Sanchez A, Chaloin O, El-Khoury R, Brabant M, Langonné A, Porceddu M, Brière JJ, Buron N, Rebouillat D, Péchoux C, Deniaud A, Brenner C, Briand JP, Muller S, Rustin P, Jacotot E . HIV-1 Tat protein directly induces mitochondrial membrane permeabilization and inactivates cytochrome c oxidase . Cell Death & Disease . 3 . 3 . 22419111 . 10.1038/cddis.2012.21 . 3317353 . 2012 . e282.
8. Beauchemin AM, Gottlieb B, Beitel LK, Elhaji YA, Pinsky L, Trifiro MA . Cytochrome c oxidase subunit Vb interacts with human androgen receptor: a potential mechanism for neurotoxicity in spinobulbar muscular atrophy . Brain Res. Bull. . 56 . 3–4 . 285–97 . 2001 . 11719263 . 10.1016/S0361-9230(01)00583-4 . 24740136 .