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Position—Specific contribution of interface tryptophans on membrane protein energetics

机译:接口色氨酸对膜蛋白能量学的定位特异性贡献

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摘要

Abstract Interface tryptophans are key residues that facilitate the folding and stability of membrane proteins. Escherichia coli OmpX possesses two unique interface tryptophans, namely Trp76, which is present at the interface and is solvent-exposed, and Trp140, which is relatively more lipid solvated than Trp76 in symmetric lipid membranes. Here, we address the requirement for tryptophan and the consequences of aromatic amino acid substitutions on the folding and stability of OmpX. Using spectroscopic measurements of OmpX-Trp/Tyr/Phe mutants, we show that the specific mutation W76→Y allows barrel assembly >1.5-fold faster than native OmpX, and increases stability by ~0.4kcalmol ?1 . In contrast, mutating W140→F/Y lowers OmpX thermodynamic stability by ~0.4kcalmol ?1 , without affecting the folding kinetics. We conclude that the stabilizing effect of tryptophan at the membrane interface can be position—and local environment—specific. We propose that the thermodynamic contributions for interface residues be interpreted with caution. Graphical abstract Display Omitted Highlights ? Interface aromatics contribute significantly to the energetics of membrane proteins. ? Role of interface Trp76 and Trp140 on stability and folding kinetics of OmpX was studied. ? Interfacial Tyr76 and buried Trp140 are energetically preferred in OmpX. ? Stabilizing mutations are not always selected during evolution.
机译:摘要界面色氨酸是促进膜蛋白的折叠和稳定性的关键残留物。大肠杆菌OMPX具有两个独特的界面色氨酸,即TRP76,其存在于界面处并且是溶剂暴露的,并且TRP140比对称脂质膜中的TRP76相对较高的脂质溶剂。在这里,我们解决了色氨酸的要求以及芳族氨基酸取代对OMPX的折叠和稳定性的后果。使用OMPX-TRP / TYR / PHE突变体的光谱测量,我们表明特定突变W76→Y允许桶组件比天然OMPX快11.5倍,并增加〜0.4kcalmol?1。相反,突变W140→F / Y通过〜0.4kcalmol?1降低OMPX热力学稳定性,而不影响折叠动力学。我们得出结论,色氨酸在膜界面处的稳定作用可以是位置和局部环境特异性。我们建议用临界残留物进行热力学贡献,谨慎地解释。图形抽象显示省略了亮点?界面芳烃对膜蛋白的能量有贡献。还研究了TRP76和TRP140对OMPX的稳定性和折叠动力学的作用。还界面TYR76和埋地TRP140在OMPX中能够精力充沛地优选。还在进化期间并不总是选择稳定突变。

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