Cytochrome c

• OMIM: 123970
• UniProt: P99999

Cytochrome c is a small protein of the family of cytochromes, which in the mitochondria during oxidative phosphorylation ( energy ) plays a crucial role as an electron carrier ( electron transporter ). Orthologs of cytochrome c occur in all living things before as mono- and multimers. In humans, mutations in the gene CYCS possible cause of cytochrome c deficiency and familial thrombocytopenia.

Structure

The primary structure of the human cytochrome C consists of 104 amino acids. Cytochrome c has a heme c as a prosthetic group that is bonded via two thioether bonds by two cysteine ​​residues in the protein. The central iron (II) ion ( Fe 2 ) is octahedral complexed via coordinative bonds to the four nitrogen atoms ( equatorial) pyrroles in porphyrin and axially to a nitrogen atom of a histidine residue and a sulfur atom of a methionine residue in the protein.

The heme group is also responsible for the red color of cytochrome c.

Function

The enzyme cytochrome c reductase ( complex III of the respiratory chain ) is oxidized to Q - cycle molecule Coenzyme Q ( CoQ ) into the inner membrane of mitochondria, thereby reducing two molecules of cytochrome c, which are located in the intermembrane space. The enzyme cytochrome c oxidase ( complex IV of the respiratory chain ) oxidized cytochrome c and four molecules thereby reducing one molecule of oxygen to give two molecules of water.

In case of damage of the mitochondrial cytochrome c is released into the cytosol through the outer membrane, where it initiates a cascade of signal programmed cell death ( apoptosis).

Since cytochrome c is present in virtually all organisms and its primary structure differs only in a few amino acids between similar species, it is an important means to the taxonomic classification of living things, and an indication of the evolutionary development of the species. Important basis for this work were published by Walter M. Fitch.