Cytochrome ''c'' oxidase subunit 5a is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

that in humans is encoded by the COX5A

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

. Cytochrome ''c'' oxidase 5A is a subunit of the

cytochrome c oxidase The enzyme cytochrome c oxidase or Complex IV (was , now reclassified as a translocasEC 7.1.1.9 is a large transmembrane protein complex found in bacteria, archaea, and the mitochondria of eukaryotes. It is the last enzyme in the Cellular respir ...

complex, also known as

Complex IV The enzyme cytochrome c oxidase or Complex IV (was , now reclassified as a translocasEC 7.1.1.9 is a large transmembrane protein complex found in bacteria, archaea, and the mitochondria of eukaryotes. It is the last enzyme in the respiratory ele ...

, the last enzyme in the

mitochondrial A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...

electron transport chain An electron transport chain (ETC) is a series of protein complexes and other molecules which transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples th ...

Structure

The COX5A gene, located on the q arm of

chromosome 15 Chromosome 15 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 15 spans about 99.7 million base pairs (the building material of DNA) and represents between 3% and 3.5% of the total DNA ...

in position 24.1, is made up of 5 exons and is 17,880 base pairs in length. The COX5A protein weighs 17 kDa and is composed of 150 amino acids. The protein is a subunit of

, which consists of 13 mitochondrial- and nuclear-encoded subunits.

Function

Cytochrome ''c'' oxidase (COX) is the terminal enzyme of the

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. Summary reaction: : 4 Fe²⁺-cytochrome ''c'' + 8 H⁺_in + O₂ → 4 Fe³⁺-cytochrome ''c'' + 2 H₂O + 4 H⁺_out

Clinical significance

COX5A (this gene) and COX5B are involved in the regulation of cancer cell metabolism by

Bcl-2 Bcl-2, encoded in humans by the ''BCL2'' gene, is the founding member of the Bcl-2 family of regulator proteins. BCL2 blocks programmed cell death (apoptosis) while other BCL2 family members can either inhibit or induce it. It was the first a ...

. COX5A interacts specifically with Bcl-2, but not with other members of the Bcl-2 family, such as Bcl-xL, Bax or Bak. The ''Trans''-activator of transcription protein (Tat) of

human immunodeficiency virus The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause AIDS, acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of th ...

(HIV) inhibits cytochrome ''c'' oxidase (COX) activity in permeabilized mitochondria isolated from both mouse and human liver, heart, and brain samples.

References

External links

*
Mass spectrometry characterization of COX5A at COPaKB
{{NLM content Proteins

Structure

Function

Clinical significance

References

Further reading

External links