COX5B

Structure

The enzyme weighs 14 kDa and is composed of 129 amino acids. 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. 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.

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

Clinical significance

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

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.

Interactions

COX5B has been shown to interact with Androgen receptor.

References

References

1. (May 1994). "Application of an automatic molecular-replacement procedure to crystal structure analysis of cytochrome c2 from Rhodopseudomonas viridis". Acta Crystallogr. D.
2. "Entrez Gene: COX5B cytochrome c oxidase subunit Vb".
3. (Oct 2013). "Integration of cardiac proteome biology and medicine by a specialized knowledgebase". Circulation Research.
4. "Cytochrome c oxidase subunit 5B, mitochondrial". Cardiac Organellar Protein Atlas Knowledgebase (COPaKB).
5. (1991). "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.
6. (1996). "The whole structure of the 13-subunit oxidized cytochrome c oxidase at 2.8 A". Science.
7. (2013). "Fundamentals of biochemistry : life at the molecular level". Wiley.
8. (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.
9. (2012). "HIV-1 Tat protein directly induces mitochondrial membrane permeabilization and inactivates cytochrome c oxidase". Cell Death & Disease.
10. (2001). "Cytochrome c oxidase subunit Vb interacts with human androgen receptor: a potential mechanism for neurotoxicity in spinobulbar muscular atrophy". Brain Res. Bull..