Chatake Toshiyuki, Ishikawa Takuya, Yanagisawa Yasuhide, Yamada Taro, Tanaka Ichiro, Fujiwara Satoru, Morimoro Yukio
Research Reactor Institute, Kyoto University, Ashashironishi 2, Kumatori, Osaka, Japan.
Acta Crystallogr Sect F Struct Biol Cryst Commun. 2011 Nov 1;67(Pt 11):1334-8. doi: 10.1107/S1744309111031903. Epub 2011 Oct 25.
Deuteration of macromolecules is an important technique in neutron protein crystallography. Solvent deuteration of protein crystals is carried out by replacing water (H(2)O) with heavy water (D(2)O) prior to neutron diffraction experiments in order to diminish background noise. The effects of solvent deuteration on the crystallization of proteinase K (PK) with polyethylene glycol as a precipitant were investigated using high-resolution X-ray crystallography. In previous studies, eight NO(3)(-) anions were included in the PK crystal unit cell grown in NaNO(3) solution. In this study, however, the PK crystal structure did not contain NO(3)(-) anions; consequently, distortions of amino acids arising from the presence of NO(3)(-) anions were avoided in the present crystal structures. High-resolution (1.1 Å) X-ray diffraction studies showed that the degradation of PK crystals induced by solvent deuteration was so small that this degradation would be negligible for the purpose of neutron protein crystallography experiments at medium resolution. Comparison of the nonhydrogen structures of nondeuterated and deuterated crystal structures demonstrated very small structural differences. Moreover, a positive correlation between the root-mean-squared differences and B factors indicated that no systematic difference existed.
大分子的氘代是中子蛋白质晶体学中的一项重要技术。在中子衍射实验之前，通过用重水（D₂O）替代水（H₂O）来对蛋白质晶体进行溶剂氘代，以减少背景噪声。使用高分辨率X射线晶体学研究了以聚乙二醇作为沉淀剂时溶剂氘代对蛋白酶K（PK）结晶的影响。在先前的研究中，在NaNO₃溶液中生长的PK晶体晶胞中包含八个NO₃⁻阴离子。然而，在本研究中，PK晶体结构不包含NO₃⁻阴离子；因此，在当前晶体结构中避免了由NO₃⁻阴离子的存在引起的氨基酸扭曲。高分辨率（1.1 Å）X射线衍射研究表明，溶剂氘代引起的PK晶体降解非常小，以至于对于中分辨率的中子蛋白质晶体学实验而言，这种降解可以忽略不计。未氘代和氘代晶体结构的非氢结构比较显示结构差异非常小。此外，均方根差异与B因子之间的正相关表明不存在系统差异。
