Structures of the substrate-binding protein provide insights into the multiple compatible solute binding specificities of the Bacillus subtilis ABC transporter OpuC
Structures of the substrate-binding protein provide insights into the multiple compatible solute binding specificities of the Bacillus subtilis ABC transporter OpuC
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底物结合蛋白的结构提供了对枯草芽孢杆菌 ABC 转运蛋白 OpuC 的多种相容溶质结合特异性的见解
DOI：
10.1042/bj20102097
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发表时间：
2011-06-01
影响因子：
4.1
通讯作者：
Chen, Yuxing
中科院分区：
文献类型：
--
作者：
Du, Yang;Shi, Wei-Wei;Chen, Yuxing
相容性溶质ABC（ATP结合盒）转运蛋白对于枯草芽孢杆菌在渗透胁迫下获得多种相容性溶质是必不可少的。 ABC 转运蛋白 OpuC 的底物结合蛋白 OpuCC（Opu 是渗透保护剂摄取）可以识别广谱的相容溶质，而其 70% 序列相同的旁系同源蛋白 OpuBC 只能结合胆碱。为了探索这种底物特异性差异的结构基础，我们分别测定了脱辅基形式的 OpuCC 以及与肉毒碱、甘氨酸甜菜碱、胆碱和四氢嘧啶复合物的晶体结构。 OpuCC 由两个 α/β/α 球状夹心结构域组成，通过两个铰链区连接，底物结合口袋位于结构域间裂缝处。底物结合后，两个结构域相互移动以捕获底物。比较结构分析揭示了一个适合各种相容溶质的塑料袋，这将多基质结合特性归因于 OpuCC。与 OpuBC 中的 Asp(96) 相比，这种可塑性是通过 OpuCC 中 Thr(94) 的单残基突变获得的功能。
The compatible solute ABC (ATP-binding cassette) transporters are indispensable for acquiring a variety of compatible solutes under osmotic stress in Bacillus subtilis. The substrate-binding protein OpuCC (Opu is osmoprotectant uptake) of the ABC transporter OpuC can recognize a broad spectrum of compatible solutes, compared with its 70% sequence-identical paralogue OpuBC that can solely bind choline. To explore the structural basis of this difference of substrate specificity, we determined crystal structures of OpuCC in the apo-form and in complex with carnitine, glycine betaine, choline and ectoine respectively. OpuCC is composed of two alpha/beta/alpha globular sandwich domains linked by two hinge regions, with a substrate-binding pocket located at the interdomain cleft. Upon substrate binding, the two domains shift towards each other to trap the substrate. Comparative structural analysis revealed a plastic pocket that fits various compatible solutes, which attributes the multiple-substrate binding property to OpuCC. This plasticity is a gain-of-function via a single-residue mutation of Thr(94) in OpuCC compared with Asp(96) in OpuBC.