Watney James B, Agarwal Pratul K, Hammes-Schiffer Sharon
Department of Chemistry, 152 Davey Laboratory, Pennsylvania State University, University Park 16802, USA.
J Am Chem Soc. 2003 Apr 2;125(13):3745-50. doi: 10.1021/ja028487u.
Hybrid quantum-classical molecular dynamics simulations of a mutant Escherichia coli dihydrofolate reductase enzyme are presented. Although residue 121 is on the exterior of the enzyme, experimental studies have shown that the mutation of Gly-121 to valine reduces the rate of hydride transfer by a factor of 163. The simulations indicate that the decrease in the hydride transfer rate for the G121V mutant is due to an increase in the free energy barrier. The calculated free energy barrier is higher for the mutant than for the wild-type enzyme by an amount that is consistent with the experimentally observed rate reduction. The calculated transmission coefficients are comparable for the wild-type and mutant enzymes. The simulations suggest that this mutation may interrupt a network of coupled promoting motions proposed to play an important role in DHFR catalysis. This phenomenon has broad implications for protein engineering and drug design.
本文展示了对突变型大肠杆菌二氢叶酸还原酶的混合量子-经典分子动力学模拟。尽管121位残基位于酶的外部，但实验研究表明，将甘氨酸-121突变为缬氨酸会使氢化物转移速率降低163倍。模拟结果表明，G121V突变体氢化物转移速率的降低是由于自由能垒的增加。计算得出的突变体自由能垒高于野生型酶，其增加量与实验观察到的速率降低一致。野生型和突变型酶的计算传输系数相当。模拟结果表明，这种突变可能会中断一个在二氢叶酸还原酶催化中起重要作用的耦合促进运动网络。这一现象对蛋白质工程和药物设计具有广泛的意义。
