ジャーナル: Nat Struct Mol Biol / 年: 2025 タイトル: Hydrophilic metformin and hydrophobic biguanides inhibit mitochondrial complex I by distinct mechanisms. 著者: Zhaoxiang He / Fei Teng / Yanqing Yang / Ruiyang Guo / Mengchen Wu / Fangzhu Han / Hongtao Tian / Jiawei Wang / Yiqi Hu / Yangwei Jiang / Leili Zhang / Chenyang Xu / Fan Yang / Jiancang Zhou ...著者: Zhaoxiang He / Fei Teng / Yanqing Yang / Ruiyang Guo / Mengchen Wu / Fangzhu Han / Hongtao Tian / Jiawei Wang / Yiqi Hu / Yangwei Jiang / Leili Zhang / Chenyang Xu / Fan Yang / Jiancang Zhou / Shan Zhang / James A Letts / Ruhong Zhou / Long Zhou / 要旨: Metformin is the only antihyperglycemic biguanide targeting type 2 diabetes mellitus with proven safety. Although a mechanism of action involving tight inhibition of the respiratory complex I has ...Metformin is the only antihyperglycemic biguanide targeting type 2 diabetes mellitus with proven safety. Although a mechanism of action involving tight inhibition of the respiratory complex I has been proposed for hydrophobic biguanides, it remains elusive for the hydrophilic metformin, whose excellent pharmacological tolerance depends on weak complex I inhibition without competitive nature. Here we solved cryo-electron microscopy structures of the metformin-bound porcine respirasome. Our structural and kinetic data are consistent with a model in which metformin enters complex I only in its open state and becomes trapped at the ubiquinone redox site by ubiquinone-induced conformational closing of the enzyme. By contrast, the hydrophobic proguanil alone occupies both the entrance and the redox site of the ubiquinone channel in open and closed complex I and is kinetically consistent with competitive inhibition with conformation-dependent affinities. Our data provide the molecular basis for metformin's well-known superior properties, such as a wide therapeutic window and positive ubiquinone cooperativity, leading to its clinical success and facilitating future therapeutic developments.