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首页> 外文期刊>Biochimica et biophysica acta. Bioenergetics >Towards the molecular mechanism of Na~+/solute symport in prokaryotes
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Towards the molecular mechanism of Na~+/solute symport in prokaryotes

机译:探讨原核生物中Na〜+ /溶质共生的分子机理

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摘要

The Na~+/solute symporter family (SSF, TC No. 2.A.21) contains more than 40 members of pro- and eukaryotic origin. Besides their sequence similarity, the transporters share the capability to utilize the free energy stored in electrochemical Na~+ gradients for the accumulation of solutes. As part of catabolic pathways most of the transporters are most probably involved in the acquisition of nutrients. Some transporters play a role in osmoadaptation. With a high resolution structure still missing, a combination of genetic, protein chemical and spectroscopic methods has been used to gain new insights into the structure and molecular mechanism of action of the transport proteins. The studies suggest a common 13-helix motif for all members of the SSF according to which the N-terminus is located in the periplasm and the C-terminus is directed into the cytoplasm (except for proteins containing a N- or C-terminal extension). Furthermore, an amino acid substitution analysis of the Na~+/proline transporter (PutP) of Escherichia coli, a member of the SSF, has identified regions of particular functional importance. For example, amino acids of TM II of PutP proved to be critical for high affinity binding of Na~+ and proline. In addition, it was shown that ligand binding induces widespread conformational alterations in the transport protein. Taken together, the studies substantiate the common idea that Na~+/solute symport is the result of a series of ligand-induced structural changes.
机译:Na〜+ /溶质同向转运蛋白家族(SSF,TC No.2.A.21)包含40多个原核和真核生物成员。除了它们的序列相似性外,转运蛋白还具有利用电化学Na〜+梯度中存储的自由能来积累溶质的能力。作为分解代谢途径的一部分,大多数转运蛋白最有可能参与营养的获取。一些转运蛋白在渗透适应中起作用。由于高分辨率结构仍然缺失,遗传,蛋白质化学和光谱学方法的组合已被用于获得对转运蛋白作用的结构和分子作用机理的新见解。研究表明,SSF的所有成员都有一个共同的13螺旋基序,根据该基序N端位于周质中,C端直接进入细胞质(含有N或C端延伸的蛋白质除外) )。此外,对作为SSF成员的大肠杆菌的Na + /脯氨酸转运蛋白(PutP)的氨基酸取代分析已经鉴定出具有特别功能重要性的区域。例如,PutP TM II的氨基酸被证明对Na +和脯氨酸的高亲和力结合至关重要。另外,已显示出配体结合诱导转运蛋白中广泛的构象改变。综上所述,这些研究证实了Na〜+ /溶质共生是一系列配体诱导的结构变化的结果的普遍观念。

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