Tang K E, Dill K A
Graduate Group in Biophysics, University of California, San Francisco 94143-1204, USA.
J Biomol Struct Dyn. 1998 Oct;16(2):397-411. doi: 10.1080/07391102.1998.10508256.
We study the fluctuations of native proteins by exact enumeration using the HP lattice model. The model fluctuations increase with temperature. We observe a low-temperature point, below which large fluctuations are frozen out. This prediction is consistent with the observation by Tilton et al. [R. F. Tilton, Jr., J. C. Dewan, and G. A. Petsko, Biochemistry 31, 2469 (1992)], that the thermal motions of ribonuclease A increase sharply above about 200 K. We also explore protein "flexibility" as defined by Debye-Waller-like factors and solvent accessibilities of core residues to hydrogen exchange. We find that proteins having greater stability tend to have fewer large fluctuations, and hence lower flexibilities. If flexibility is necessary for enzyme catalysis, this could explain why proteins from thermophilic organisms, which are exceptionally stable, may be catalytically inactive at normal temperatures.
我们使用HP晶格模型通过精确枚举来研究天然蛋白质的涨落。模型涨落随温度升高。我们观察到一个低温点，低于该温度时大的涨落被冻结。这一预测与蒂尔顿等人的观察结果一致[小R.F. 蒂尔顿、J.C. 德万和G.A. 佩茨科，《生物化学》31, 2469 (1992)]，即核糖核酸酶A的热运动在约200 K以上急剧增加。我们还探讨了由类德拜-瓦勒因子和核心残基对氢交换的溶剂可及性所定义的蛋白质“柔韧性”。我们发现稳定性更高的蛋白质往往具有更少的大涨落，因此柔韧性更低。如果柔韧性对于酶催化是必要的，这可以解释为什么来自嗜热生物的蛋白质异常稳定，却可能在常温下无催化活性。
