文章基本信息

标题：Unveiling the gating mechanism of ECF Transporter RibU
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作者：Jianing Song ; Changge Ji ; John Z. H. Zhang 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2013
卷号：3
期号：1
DOI：10.1038/srep03566
语种：English
出版社：Springer Nature
摘要：Energy-coupling factor (ECF) transporters are responsible for uptake of micronutrients in prokaryotes. The recently reported crystal structure of an ECF transporter RibU provided a foundation for understanding the structure and transport mechanism of ECF transporters. In the present study, molecular dynamics (MD) was carried out to study the conformational changes of the S component RibU upon binding by riboflavin. Our result and analysis revealed a critically important gating mechanism, in which part of loop5 (L5′) (eleven residues, missing in the crystal structure) between TM5 and TM6 is dynamically flexible and serves as a gate. Specifically, the L5′ opens a large cavity accessible to riboflavin from the extracellular space in Apo-RibU and closes the cavity upon riboflavin binding through hydrophobic packing with riboflavin. Thus, L5′is proposed to be the gate for riboflavin binding. In addition, steered molecular dynamics (SMD) simulation is employed to investigate the translocation dynamics of RibU during riboflavin transport. The simulation result does not show evidence that the S component alone can carry out the transport function. Since loop regions are very flexible and therefore could not be resolved by crystallography, their dynamics are hard to predict based on crystal structure alone.