COX5A
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. Structure. 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. The COX5A protein weighs 17 kDa and is composed of 150 amino acids. The protein is a subunit of Complex IV, which consists of 13 mitochondrial- and  nuclear-encoded subunits. 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 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: Clinical significance. 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. 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.