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标题：The mechanism of transport by mitochondrial carriers based on analysis of symmetry
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作者：Alan J. Robinson ; Catherine Overy ; Edmund R. S. Kunji 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2008
卷号：105
期号：46
页码：17766-17771
DOI：10.1073/pnas.0809580105
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The structures of mitochondrial transporters and uncoupling proteins are 3-fold pseudosymmetrical, but their substrates and coupling ions are not. Thus, deviations from symmetry are to be expected in the substrate and ion-binding sites in the central aqueous cavity. By analyzing the 3-fold pseudosymmetrical repeats from which their sequences are made, conserved asymmetric residues were found to cluster in a region of the central cavity identified previously as the common substrate-binding site. Conserved symmetrical residues required for the transport mechanism were found at the water-membrane interfaces, and they include the three PX[DE]XX[RK] motifs, which form a salt bridge network on the matrix side of the cavity when the substrate-binding site is open to the mitochondrial intermembrane space. Symmetrical residues in three [FY][DE]XX[RK] motifs are on the cytoplasmic side of the cavity and could form a salt bridge network when the substrate-binding site is accessible from the mitochondrial matrix. It is proposed that the opening and closing of the carrier may be coupled to the disruption and formation of the 2 salt bridge networks via a 3-fold rotary twist induced by substrate binding. The interaction energies of the networks allow members of the transporter family to be classified as strict exchangers or uniporters.
关键词：membrane proteins ; substrate binding ; amino acid sequence analysis ; salt bridge networks ; conformational changes