Cytochrome b-c1 complex subunit 6, mitochondrial

UQCRH (cytochrome b-c1 complex subunit 6, mitochondrial) is a small 91-amino-acid protein encoded by the UQCRH gene (UniProt: P07919). It functions as a component of the ubiquinol-cytochrome c oxidoreductase (complex III) in the mitochondrial electron transport chain, catalyzing electron transfer from ubiquinol to cytochrome c while coupling proton translocation across the inner mitochondrial membrane to support oxidative phosphorylation and ATP synthesis (UniProt: P07919).

UQCRH is localized to the mitochondrial membrane and participates in the Q-cycle mechanism of electron transport. Pathogenic mutations cause mitochondrial complex III deficiency, nuclear type 11 (MC3DN11; MIM 620137), an autosomal recessive condition characterized by recurrent lactic acidosis, hyperammonemia, and encephalopathy (UniProt: P07919).

UQCRH shows Alzheimer's Disease relevance with elevated expression in post-mortem AD brain tissue. Proteomics analysis of human AD brain versus age-matched controls revealed upregulation of UQCRH (mean log2 fold-change: 1.52; Chaparral AD proteomics), suggesting potential involvement in AD-related mitochondrial dysfunction or bioenergetic stress in the diseased brain.