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Chestnut Studying 摘要 Mitochondria serve a crucial role in cell growth and proliferation by supporting both ATP synthesis and the production of macromolecular precursors. Whereas oxidative phosphorylation (OXPHOS) depends mainly on the oxidation of intermediates from the tricarboxylic acid cycle, the mitochondrial production of proline and ornithine relies on reductive synthesis. How these competing metabolic pathways take place in the same organelle is not clear. Here we show that when cellular dependence on OXPHOS increases, pyrroline-5-carboxylate synthase (P5CS)—the rate-limiting enzyme in the reductive synthesis of proline and ornithine—becomes sequestered in a subset of mitochondria that lack cristae and ATP synthase. This sequestration is driven by both the intrinsic ability of P5CS to form filaments and the mitochondrial fusion and fission cycle. Disruption of mitochondrial dynamics, by impeding mitofusin-mediated fusion or dynamin-like-protein-1-mediated fis
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