COX6B1

Cytochrome c oxidase subunit 6B1 is an is_associated_with::enzyme that in humans is encoded by the COX6B1 is_associated_with::gene. Cytochrome c oxidase 6B1 is a subunit of the cytochrome c oxidase complex, also known as is_associated_with::Complex IV, the last enzyme in the mitochondrial is_associated_with::electron transport chain. Mutations of the COX6B1 gene are associated with severe infantile is_associated_with::encephalomyopathy and mitochondrial complex IV deficiency (MT-C4D).

Structure
The COX6B1 gene, located on the q arm of is_associated_with::chromosome 19 in position 13.1, contains 4 is_associated_with::exons and is 10,562 is_associated_with::base pairs in length. The COX6B1 protein weighs 10 kDa and is composed of 86 amino acids. The protein is a subunit of is_associated_with::Complex IV, a heteromeric complex consisting of 3 catalytic subunits encoded by mitochondrial genes and multiple structural subunits encoded by nuclear genes.

Function
Cytochrome c oxidase (COX), the terminal enzyme of the is_associated_with::mitochondrial respiratory chain, catalyzes the electron transfer from reduced cytochrome c to oxygen. It is a heteromeric complex consisting of 3 catalytic subunits encoded by mitochondrial genes and multiple structural subunits encoded by nuclear genes. The mitochondrially-encoded subunits function in electron transfer, and the nuclear-encoded subunits may be involved in the regulation and assembly of the complex. This nuclear gene encodes subunit VIb. Three pseudogenes COX6BP-1, COX6BP-2 and COX6BP-3 have been found on chromosomes 7, 17 and 22q13.1-13.2, respectively.

Summary reaction:
 * 4 Fe2+-cytochrome c + 8 H+in + O2 → 4 Fe3+-cytochrome c + 2 H2O + 4 H+out

Clinical significance
Mutations affecting the COX6B1 gene are associated with mitochondrial complex IV deficiency (MT-C4D), a disorder of the mitochondrial respiratory chain with heterogeneous clinical manifestations, ranging from isolated is_associated_with::myopathy to severe multisystem disease affecting several tissues and organs. Features include is_associated_with::hypertrophic is_associated_with::cardiomyopathy, is_associated_with::hepatomegaly and is_associated_with::liver dysfunction, is_associated_with::hypotonia, muscle weakness, exercise intolerance, developmental delay, delayed motor development and mental retardation. Some affected individuals manifest a fatal hypertrophic cardiomyopathy resulting in neonatal death. A subset of patients manifest is_associated_with::Leigh's syndrome.