CYTB encodes cytochrome b, a core component of the ubiquinol-cytochrome c reductase complex (complex III) in the mitochondrial respiratory chain. It mediates electron transfer from ubiquinol to cytochrome c and contributes to proton gradient generation essential for ATP synthesis 1. Beyond its classical respiratory function, CYTB transcripts encode a previously unrecognized 187-amino-acid protein (CYTB-187AA) through cytosolic translation, which localizes to the mitochondrial matrix and regulates pluripotency and fertility by modulating ATP production via interaction with SLC25A3 1. CYTB mutations impair mitochondrial translation, particularly affecting proteins with high phenylalanine content, leading to respiratory complex dysfunction, reduced membrane potential, and increased reactive oxygen species production 2. These defects underlie pathological conditions including cardiomyopathy and deafness through impaired mitochondrial bioenergetics and autophagy dysregulation. Clinically, CYTB serves as a therapeutic target for malaria control; endochin-like quinolones inhibiting the cytochrome bc1 complex demonstrate potent antiparasitic activity in insecticide-resistant mosquitoes 3. Additionally, CYTB sequence variation has applications in population genetics and species identification across diverse organisms 45. The gene's dual role in oxidative phosphorylation and novel protein translation establishes it as multifunctional in cellular energy metabolism and development.