The V-motifs facilitate the substrate capturing step of the PTS elevator mechanism

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• 作者：Ake Vastermark^a ; ^{msaier@ucsd.edu" class="auth_mail" title="E-mail the corresponding author} ; Adelle Driker^a ; Jingwei Weng^b ; Xiaochun Li^c ; Jiawei Wang^d ; Milton H. Saier^a
• 关键词：C2A ; P21A ; space group names ; APC ; Amino acid-Polyamine organoCation superfamily of secondary carriers ; PTS ; bacterial Phospho-Transferase System ; NMA ; Normal Mode Analysis
• 刊名：Journal of Structural Biology
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：196
• 期：3
• 页码：496-502
• 全文大小：2257 K

文摘

We propose that the alternative crystal forms of outward open UlaA (which are experimental, not simulated, and contain the substrate in the cavity) can be used to interpret/validate the MD results from MalT (the substrate capture step, which involves the mobile second TMSs of the V-motifs, TMSs 2 and 7). Since the crystal contacts are the same between the two alternative crystal forms of outward open UlaA, the striking biological differences noted, including rearranged hydrogen bonds and salt bridge coordination, are not attributable to crystal packing differences. Using transport assays, we identified G58 and G286 as essential for normal vitamin C transport, but the comparison of alternative crystal forms revealed that these residues to unhinge TMS movements from substrate-binding side chains, rendering the mid-TMS regions of homologous TMSs 2 and 7 relatively immobile. While the TMS that is involved in substrate binding in MalT is part of the homologous bundle that holds the two separate halves of the transport assembly (two proteins) together, an unequal effect of the two knockouts was observed for UlaA where both V-motifs are free from such dimer interface interactions.