COX7B

Description

The COX7B (cytochrome c oxidase subunit 7B) is a protein-coding gene located on chromosome X.

Cytochrome c oxidase subunit 7B, mitochondrial (COX7B) is an enzyme encoded by the COX7B gene in humans. COX7B is a nuclear-encoded subunit of cytochrome c oxidase (COX), 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. COX7B is the terminal enzyme of the mitochondrial respiratory chain. Work with Oryzias latices has linked disruptions in COX7B with microphthalmia with linear skin lesions (MLS), microcephaly, and mitochondrial disease. Clinically, mutations in COX7B have been associated with linear skin defects with multiple congenital anomalies. COX7B is located on the q arm of the X chromosome in position 21.1 and has 3 exons. The COX7B gene produces a 9.2 kDa protein composed of 80 amino acids. COX7B is one of the nuclear-encoded polypeptide chains of cytochrome c oxidase (COX), a heteromeric complex consisting of 3 catalytic subunits encoded by mitochondrial genes and multiple structural subunits encoded by nuclear genes. The protein encoded by COX7B belongs to the cytochrome c oxidase VIIb family. COX7B has a 24 amino acid transit peptide domain from positions 1-24, an 8 amino acid topological mitochondrial matrix domain from positions 25–32, a helical, 27 amino acid transmembrane domain from positions 33–59, and a 21 amino acid topological intermembrane domain from positions 60–80.

COX7B is a crucial component of cytochrome c oxidase (complex IV), the final enzyme in the mitochondrial electron transport chain that drives oxidative phosphorylation. This chain consists of three multi-subunit complexes: succinate dehydrogenase (complex II), ubiquinol-cytochrome c oxidoreductase (complex III), and cytochrome c oxidase (complex IV). These complexes work together to transfer electrons derived from NADH and succinate to molecular oxygen, generating an electrochemical gradient across the inner mitochondrial membrane. This gradient powers transmembrane transport and ATP synthase. Cytochrome c oxidase is responsible for catalyzing the reduction of oxygen to water. Electrons from reduced cytochrome c in the intermembrane space are transferred through the dinuclear copper A center of subunit 2 and heme A of subunit 1 to the active site in subunit 1. This active site, a binuclear center, utilizes heme A3 and copper B to reduce molecular oxygen to two water molecules, using four electrons from cytochrome c and four protons from the mitochondrial matrix. COX7B plays a role in proper central nervous system development in vertebrates.

COX7B is also known as APLCC, LSDMCA2.

Associated Diseases

• Linear skin defects with multiple congenital anomalies 2
• Linear skin defects with multiple congenital anomalies 1
• Microphthalmia with linear skin defects syndrome