The MT-CYB gene is located on the p arm of mitochondrial DNA in position 12 and spans 1,140 base pairs.

[11] Complex III is responsible for the catalysis of electron transfer from coenzyme Q to cytochrome c in the mitochondrial respiratory chain by translocating protons concomitantly across the inner membrane of the mitochondria.

[12][9] The transfer of electrons then contributes to the generation of a proton gradient across the mitochondrial membrane that is then used for ATP synthesis.

A complex III deficiency can result in a highly variable phenotype depending on which tissues are affected.

[9][10] Complex III deficiency is known to be rare among mitochondrial diseases and may follow a maternal or mendelian mode of inheritance due to its duality of genetic origin.