Roy Arijit, Taraphder Srabani
Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India.
Biopolymers. 2006 Aug 15;82(6):623-30. doi: 10.1002/bip.20516.
We have investigated the possible proton transfer pathways from the surface of the protein to the zinc-bound water molecule in the mutant His-64-Ala of human carbonic anhydrase II. Starting with an input of known crystallographic structures of the mutant, we model the proton pathways as hydrogen-bonded networks of proton conducting groups and bound solvent molecules. No proton path is detected in the mutant, in close agreement with the experimental observation of a 20-fold decrease in its catalytic efficiency compared to the wild-type enzyme. We also investigate in detail changes in hydration structure at the active site of the mutant and the resulting proton paths in the presence of an exogenous proton donor 4-methylimidazole (4-MI). The proton transfer pathways thus detected are correlated to the observed chemical rescue of catalytic activity by 4-MI.
我们研究了人类碳酸酐酶II的突变体His-64-Ala中质子从蛋白质表面转移至与锌结合的水分子的可能途径。从该突变体已知的晶体结构输入开始，我们将质子途径模拟为质子传导基团和结合溶剂分子的氢键网络。在该突变体中未检测到质子路径，这与实验观察结果密切相符，即与野生型酶相比，其催化效率降低了20倍。我们还详细研究了突变体活性位点处水合结构的变化以及在外源质子供体4-甲基咪唑（4-MI）存在下产生的质子路径。由此检测到的质子转移途径与观察到的4-MI对催化活性的化学拯救相关。
