Conformational Dynamics Govern the Free-Energy Landscape of a Membrane-Interacting Protein
Conformational Dynamics Govern the Free-Energy Landscape of a Membrane-Interacting Protein
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DOI：
10.1021/acsomega.8b01609
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发表时间：
2018-09-01
期刊：
影响因子：
4.1
通讯作者：
Keller, Sandro
中科院分区：
文献类型：
--
作者：
Frotscher, Erik;Krainer, Georg;Keller, Sandro
膜结合蛋白质的平衡稳定性和折叠速率由与其环境的疏水性和极性分子间接触以及分子内堆积和构象动力学决定。然而，这些因素的贡献仍然难以捉摸，并且可能在蛋白质之间存在很大差异。来自枯草芽孢杆菌的Mistic是一个特别有趣的α-螺旋蛋白的例子，尽管它具有不寻常的亲水性，但它与膜相关。在胶束中，Mistic通过与去污剂的疏水和极性相互作用来稳定，但目前尚不清楚这些分子间接触是否以及如何与蛋白质本身的结构和动态适应相结合。在这里，我们研究了包装和构象动力学的Mistic作为洗涤剂头基化学和链长的函数，采用单分子福斯特共振能量转移光谱和时间分辨的固有色氨酸荧光光谱。令人惊讶的是，在非离子型洗涤剂，更有效的疏水埋葬，因此，更大的蛋白质稳定性与疏水胶束厚度的增加伴随着逐渐松动的螺旋束。相比之下，发现Mistic在两性离子洗涤剂中呈现稳定的紧凑折叠，其允许在纳秒时间尺度上更快的动力学。因此，分子内包装本身不足以赋予高蛋白质稳定性;相反，增强的纳秒动力学，因此，更大的构象熵在紧凑的折叠状态占Mistic的高平衡稳定性和快速的折叠速率在两性离子胶束，即使在不太有效的疏水埋葬的代价。
The equilibrium stabilities and the folding rates of membrane-bound proteins are determined by hydrophobic and polar intermolecular contacts with their environment as well as by intramolecular packing and conformational dynamics. The contributions of these factors, however, remain elusive and might vary considerably among proteins. Mistic from Bacillus subtilis is a particularly intriguing example of an alpha-helical protein that associates with membranes in spite of its unusual hydrophilicity. In micelles, Mistic is stabilized by hydrophobic and polar interactions with detergents, but it is unclear whether and how these intermolecular contacts are coupled to structural and dynamic adaptations of the protein itself. Here, we investigated the packing and the conformational dynamics of Mistic as functions of detergent headgroup chemistry and chain length, employing single-molecule Forster resonance energy transfer spectroscopy and time-resolved intrinsic tryptophan fluorescence spectroscopy. Surprisingly, in nonionic detergents, more effective hydrophobic burial and, thus, greater protein stability with increasing hydrophobic micellar thickness were accompanied by a gradual loosening of the helical bundle. By contrast, Mistic was found to assume a stable, compact fold in zwitterionic detergents that allowed faster dynamics on the nanosecond timescale. Thus, intramolecular packing per se is insufficient for conferring high protein stability; instead, enhanced nanosecond dynamics and, consequently, greater conformational entropy in the compact folded state account for Mistic's high equilibrium stability and fast folding rates in zwitterionic micelles even at the expense of less effective hydrophobic burial.