Usher K C, de la Cruz A F, Dahlquist F W, Swanson R V, Simon M I, Remington S J
Institute of Molecular Biology and Department of Chemistry, University of Oregon, Eugene 97403, USA.
Protein Sci. 1998 Feb;7(2):403-12. doi: 10.1002/pro.5560070221.
The crystal structure of CheY protein from Thermotoga maritima has been determined in four crystal forms with and without Mg++ bound, at up to 1.9 A resolution. Structural comparisons with CheY from Escherichia coli shows substantial similarity in their folds, with some concerted changes propagating away from the active site that suggest how phosphorylated CheY, a signal transduction protein in bacterial chemotaxis, is recognized by its targets. A highly conserved segment of the protein (the "y-turn loop," residues 55-61), previously suggested to be a rigid recognition determinant, is for the first time seen in two alternative conformations in the different crystal structures. Although CheY from Thermotoga has much higher thermal stability than its mesophilic counterparts, comparison of structural features previously proposed to enhance thermostability such as hydrogen bonds, ion pairs, compactness, and hydrophobic surface burial would not suggest it to be so.
嗜热栖热菌（Thermotoga maritima）CheY蛋白的晶体结构已通过四种晶体形式确定，有或没有结合Mg++，分辨率高达1.9 Å。与大肠杆菌CheY的结构比较表明，它们的折叠结构有很大相似性，一些协同变化从活性位点向外传播，这表明细菌趋化作用中的信号转导蛋白磷酸化CheY是如何被其靶标识别的。该蛋白高度保守的一段（“y-turn环”，第55 - 61位氨基酸残基），以前被认为是一个刚性识别决定因素，首次在不同晶体结构中以两种不同构象出现。尽管嗜热栖热菌的CheY比其嗜温同类具有更高的热稳定性，但比较先前提出的增强热稳定性的结构特征，如氢键、离子对、紧密性和疏水表面埋藏，却无法说明其如此稳定的原因。
