Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6059, USA.
Protein Sci. 2012 Jul;21(7):987-95. doi: 10.1002/pro.2082. Epub 2012 Jun 11.
To investigate the determinants of protein hydrogen exchange (HX), HX rates of most of the backbone amide hydrogens of Staphylococcal nuclease were measured by NMR methods. A modified analysis was used to improve accuracy for the faster hydrogens. HX rates of both near surface and well buried hydrogens are spread over more than 7 orders of magnitude. These results were compared with previous hypotheses for HX rate determination. Contrary to a common assumption, proximity to the surface of the native protein does not usually produce fast exchange. The slow HX rates for unprotected surface hydrogens are not well explained by local electrostatic field. The ability of buried hydrogens to exchange is not explained by a solvent penetration mechanism. The exchange rates of structurally protected hydrogens are not well predicted by algorithms that depend only on local interactions or only on transient unfolding reactions. These observations identify some of the present difficulties of HX rate prediction and suggest the need for returning to a detailed hydrogen by hydrogen analysis to examine the bases of structure-rate relationships, as described in the companion paper (Skinner et al., Protein Sci 2012;21:996-1005).
为了研究蛋白质氢交换（HX）的决定因素，通过 NMR 方法测量了枯草溶菌素的大部分骨架酰胺氢的 HX 速率。使用改进的分析方法来提高更快氢的准确性。近表面和深埋氢的 HX 速率分布在 7 个数量级以上。将这些结果与以前的 HX 速率确定假设进行了比较。与普遍假设相反，接近天然蛋白质的表面通常不会产生快速交换。未保护的表面氢的缓慢 HX 速率不能很好地用局部静电场来解释。埋藏氢的可交换性不能用溶剂渗透机制来解释。仅依赖于局部相互作用或仅依赖于瞬时展开反应的算法并不能很好地预测结构保护氢的交换速率。这些观察结果确定了 HX 速率预测的一些当前困难，并表明需要返回详细的逐氢分析，以检查结构-速率关系的基础，如随附论文所述（Skinner 等人，蛋白质科学 2012 年；21:996-1005）。
