Yamagata Y, Kubota M, Sumikawa Y, Funahashi J, Takano K, Fujii S, Yutani K
Institute for Protein Research, Faculty of Pharmaceutical Sciences, Osaka University, Japan.
Biochemistry. 1998 Jun 30;37(26):9355-62. doi: 10.1021/bi980431i.
The contribution of hydrogen bonds to the conformational stability of human lysozyme was investigated by the combination of calorimetric and X-ray analyses of six Tyr --> Phe mutants. Unfolding Delta G and unfolding Delta H values of the Tyr --> Phe mutant proteins were changed by from +0.3 to -4.0 kJ/mol and from 0 to -16 kJ/mol, respectively, compared to those of the wild-type protein. The net contribution of a hydrogen bond at a specific site to stability (Delta Gwild/HB), considering factors affected by substitutions, was evaluated on the basis of X-ray structures of the mutant proteins. In the present study, one of six mutant proteins was suitable for evaluating the strength of the hydrogen bond. Delta Gwild/HB for the intramolecular hydrogen bond at Tyr124 was evaluated to be 7.5 kJ/mol. Results of the analysis of other mutants also suggest that hydrogen bonds of the hydroxyl group of Tyr, including the hydrogen bond with a water molecule, contribute to the stabilization of the human lysozyme.
通过对六个酪氨酸（Tyr）突变为苯丙氨酸（Phe）的突变体进行量热分析和X射线分析相结合的方法，研究了氢键对人溶菌酶构象稳定性的贡献。与野生型蛋白相比，Tyr→Phe突变体蛋白的解折叠自由能变化（ΔG）和解折叠焓变（ΔH）分别从+0.3至 -4.0 kJ/mol和从0至 -16 kJ/mol发生了改变。基于突变体蛋白的X射线结构，考虑到取代所影响的因素，评估了特定位点氢键对稳定性的净贡献（ΔGwild/HB）。在本研究中，六个突变体蛋白之一适合用于评估氢键的强度。Tyr124处分子内氢键的ΔGwild/HB经评估为7.5 kJ/mol。对其他突变体的分析结果也表明，酪氨酸羟基的氢键，包括与水分子形成的氢键，有助于人溶菌酶的稳定。
