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AliasesCOX5A, COX, COX-VA, VA, cytochrome c oxidase subunit 5A
External IDsMGI: 88474 HomoloGene: 37905 GeneCards: COX5A
Gene location (Human)
Chromosome 15 (human)
Chr.Chromosome 15 (human)[1]
Chromosome 15 (human)
Genomic location for COX5A
Genomic location for COX5A
Band15q24.2Start74,919,791 bp[1]
End74,938,083 bp[1]
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC)Chr 15: 74.92 – 74.94 MbChr 9: 57.52 – 57.53 Mb
PubMed search[3][4]
View/Edit HumanView/Edit Mouse

Cytochrome c oxidase subunit 5a is a protein that in humans is encoded by the COX5A gene. Cytochrome c oxidase 5A is a subunit of the cytochrome c oxidase complex, also known as Complex IV, the last enzyme in the mitochondrial electron transport chain.[5]


The COX5A gene, located on the q arm of chromosome 15 in position 24.1, is made up of 5 exons and is 17,880 base pairs in length.[5] The COX5A protein weighs 17 kDa and is composed of 150 amino acids.[6][7] The protein is a subunit of Complex IV, which consists of 13 mitochondrial- and nuclear-encoded subunits.[5]


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 molecular 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.[5]

Summary reaction:

4 Fe2+-cytochrome c + 8 H+in + O2 → 4 Fe3+-cytochrome c + 2 H2O + 4 H+out[8]

Clinical significance[edit]

COX5A (this gene) and COX5B are involved in the regulation of cancer cell metabolism by Bcl-2. COX5A interacts specifically with Bcl-2, but not with other members of the Bcl-2 family, such as Bcl-xL, Bax or Bak.[9]

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.[10]


  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000178741 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000000088 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:".
  4. ^ "Mouse PubMed Reference:".
  5. ^ a b c d "Entrez Gene: Cytochrome c oxidase subunit Va".
  6. ^ Zong NC, Li H, Li H, Lam MP, Jimenez RC, Kim CS, Deng N, Kim AK, Choi JH, Zelaya I, Liem D, Meyer D, Odeberg J, Fang C, Lu HJ, Xu T, Weiss J, Duan H, Uhlen M, Yates JR, Apweiler R, Ge J, Hermjakob H, Ping P (Oct 2013). "Integration of cardiac proteome biology and medicine by a specialized knowledgebase". Circulation Research. 113 (9): 1043–53. doi:10.1161/CIRCRESAHA.113.301151. PMC 4076475. PMID 23965338.
  7. ^ "Cytochrome c oxidase subunit 5a". Cardiac Organellar Protein Atlas Knowledgebase (COPaKB).
  8. ^ Voet D, Voet JG, Pratt CW (2013). "Chapter 18". Fundamentals of biochemistry: life at the molecular level (4th ed.). Hoboken, NJ: Wiley. pp. 581–620. ISBN 978-0-470-54784-7.
  9. ^ Chen ZX, Pervaiz S (Mar 2010). "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. doi:10.1038/cdd.2009.132. PMID 19834492.
  10. ^ 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 (2012). "HIV-1 Tat protein directly induces mitochondrial membrane permeabilization and inactivates cytochrome c oxidase". Cell Death & Disease. 3 (3): e282. doi:10.1038/cddis.2012.21. PMC 3317353. PMID 22419111.

Further reading[edit]

External links[edit]

This article incorporates text from the United States National Library of Medicine, which is in the public domain.