{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nMitochondrial cytochrome b (MT‑CYB) is a core subunit of complex III of the electron transport chain, serving as a pivotal mediator of electron transfer from ubiquinol to cytochrome c and thereby driving the proton‐motive force essential for ATP synthesis. Its precise assembly and function are critical for optimal mitochondrial bioenergetics, and mutations in MT‑CYB have been shown to disrupt complex III activity—often leading to isolated enzyme deficiencies, impaired oxidative phosphorylation, and altered apoptotic signaling. In patients, such mutations manifest as exercise intolerance, neuromuscular and multisystem involvement, and even tissue‐specific defects such as sensorineural hearing loss. Furthermore, studies employing biochemical, genetic, and functional assays have underscored the importance of MT‑CYB integrity not only for energy production but also for maintaining structural interactions with other respiratory complexes, as well as for modulating stress‐ and redox‐sensitive transcriptional responses."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "13"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nBeyond its indispensable role in cellular energy metabolism, variations in the MT‑CYB gene have been implicated in a broad spectrum of pathological conditions. Altered MT‑CYB function can compromise sperm mitochondrial activity—contributing to asthenozoospermia, fertilization failure, and male infertility—as well as participate in the pathogenesis of obesity‐related phenotypes. In addition, MT‑CYB mutations and sequence variations have been associated with diverse disease processes including certain cancers, atherosclerosis, fibromyalgia, and even aberrant immune responses; in one example, proteolytic fragments of cytochrome b have been shown to act as cryptides that activate neutrophils. These findings collectively highlight the dual importance of MT‑CYB both as an essential bioenergetic enzyme and as a modulator of cellular signaling and disease susceptibility."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "14", "end_ref": "26"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Tatsuya Yamasoba, Yu ichi Goto, Yoshitomo Oka, et al. 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