Cytochrome c oxidase subunit 4 isoform 2, mitochondrial (COX4I2)

Cytochrome c oxidase subunit 4 isoform 2 (COX4I2) is a nuclear-encoded structural subunit of complex IV (cytochrome c oxidase) in the mitochondrial electron transport chain[1][2]. It functions as a regulator of oxidative phosphorylation, facilitating electron transfer from cytochrome c to oxygen—the terminal step in ATP generation. The two isoforms of subunit IV, COX4I1 and COX4I2, enable tissue-specific and oxygen level-dependent optimization of mitochondrial respiration; COX4I2 is upregulated under low oxygen conditions (hypoxia), especially in placenta and lung tissues, and contributes to the adaptation of cellular energy metabolism[1][3]. Mutations in COX4I2 are associated with rare syndromic diseases affecting the exocrine pancreas, blood cells, and bone formation[2]. No drugs directly and specifically target COX4I2, but the entire cytochrome c oxidase complex is affected by certain poisons and metabolic inhibitors[1][2]. COX4I2 expression levels may offer potential as a biomarker for hypoxia adaptation and studies suggest a role in regulating reactive oxygen species (ROS) production under basal and hypoxic conditions[3]. Safety concerns with therapeutic targeting involve the risk of mitochondrial activity disruption, broad energetic consequences, and systemic toxicity.

Other names

Cytochrome c oxidase subunit 4 isoform 2, mitochondrialCOX4I2COX4L2COX IV-2COXIV-2COX4BdJ857M17.2COX4-2Cytochrome c oxidase subunit IV isoform 2Cytochrome c oxidase subunit IV-like 2COX4

Inhibition of electron transfer (for cytochrome c oxidase inhibitors); Modulation of oxygen sensing through altered subunit composition