Cytochrome c1, heme protein, mitochondrial

Cytochrome c1 (CYC1) is a heme-containing catalytic core subunit of the mitochondrial ubiquinol-cytochrome c oxidoreductase complex (complex III) of the electron transport chain (UniProt: P08574). It transfers electrons from the Rieske protein's iron-sulfur cluster to cytochrome c, directly coupling electron transfer to proton translocation across the inner mitochondrial membrane during oxidative phosphorylation.

CYC1 is expressed in mitochondria-rich tissues and is essential for cellular energy production. Loss-of-function mutations cause mitochondrial complex III deficiency, an autosomal recessive disorder marked by lactic acidosis, hyperglycemia, and impaired neurological function (UniProt: P08574). This connection underscores the protein's critical role in metabolic homeostasis.

In Alzheimer's disease, CYC1 is upregulated in post-mortem AD brain tissue compared to age-matched controls (Chaparral AD proteomics), with a mean log₂ fold-change of 1.34 across subcellular fractions. This elevation suggests potential compensatory mitochondrial respiratory activity in AD pathology or altered energy metabolism associated with neurodegeneration.