The effect of salt on the conformations of three model proteins is revealed by variable temperature ion mobility mass spectrometry
The effect of salt on the conformations of three model proteins is revealed by variable temperature ion mobility mass spectrometry
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DOI：
10.1016/j.ijms.2013.02.005
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发表时间：
2013-07-01
影响因子：
1.8
通讯作者：
Barran, Perdita E.
中科院分区：
文献类型：
--
作者：
Berezovskaya, Yana;Porrini, Massimiliano;Barran, Perdita E.
三种不同分子质量的“模型”蛋白质：溶菌酶、细胞色素C和BPTI与碘化钠孵育，并在纳米喷雾电离后，使用漂移管离子迁移质谱（DT IM-MS）确定它们的气相构象。离子迁移率测量是在三种不同的漂移细胞温度下进行的，以氦作为缓冲气体——“环境”（300 K）、“冷”（260 K）和“热”（360 K）。在所有三种蛋白质上都观察到显著水平的碘化物内合，碘化物的数量与可用碱性位点的数量相关。在盐的存在下，每种蛋白质所占据的构象空间发生了改变，这表现为每种蛋白质在高电荷态和低电荷态的内合物强度的降低。这种“盐入”减少了溶菌酶和BTPI的CCS扩散，使其收敛于从晶体结构数据计算的值。观察到所有蛋白质的构象变化是电荷状态的函数，这归因于库仑驱动的展开。在碘化物存在的情况下，热诱导展开（在冷和热温度下都能观察到）被最小化。这是关于蛋白质在气相中“冷变性”的第一份报告，并表明这种效应可能是蛋白质折叠固有的。(C) 2013 Elsevier B.V.版权所有
Three 'model' proteins of varying molecular mass: lysozyme, cytochrome C, and BPTI are incubated with sodium iodide and following nano-spray ionisation, their gas-phase conformations are determined using drift tube ion mobility mass spectrometry (DT IM-MS). Ion mobility measurements were carried out on these proteins with helium as the buffer gas at three different drift cell temperatures - 'ambient' (300 K), 'cold' (260 K) and 'hot' (360 K). Significant levels of adducted iodide are observed on all three proteins with the number of iodides correlating to the number of available basic sites. The conformational space occupied by each protein is altered in the presence of salt, this is exhibited by a reduction in the intensities of adducted species for high and low charge states for each protein. This 'salting in' reduces the CCS spread for lysozyme and BTPI to converge on the values calculated from the crystal structure data. A change in conformation of all proteins is observed as a function of charge state, which is attributed to coulombically driven unfolding. Thermally induced unfolding (which is observed at both cold and hot temperatures) is minimised in the presence of adducted iodide. This is the first report of 'cold denaturisation' for proteins in the gas phase and suggests that this effect maybe intrinsic to the protein fold. (C) 2013 Elsevier B.V. All rights reserved.