Steinbach P J, Brooks B R
Laboratory of Structural Biology, National Institutes of Health, Bethesda, MD 20892, USA.
Proc Natl Acad Sci U S A. 1996 Jan 9;93(1):55-9. doi: 10.1073/pnas.93.1.55.
To characterize the functionally important anharmonic motions of proteins, simulations of carboxymyoglobin (MbCO) dynamics have been performed during which dihedral transitions were prohibited. Comparison of torsionally restrained and unrestrained protein dynamics simulated at three levels of hydration and at temperatures ranging from 100 to 400 K suggests that hydration "catalyzes" protein mobility by facilitating collective anharmonic motions that do not require dihedral transitions. When dihedral transitions were prohibited, dehydrated MbCO, to a good approximation, exhibited only harmonic fluctuations, whereas hydrated MbCO exhibited both harmonic and anharmonic motions. The fluctuation of helix centers of mass also remained highly anharmonic in the torsionally restrained hydrated system. Atomic mean-square fluctuation at 300 K was reduced upon prohibition of dihedral transitions by only 28% and 10% for MbCO hydrated by 350 and 3830 water molecules, respectively.
为了表征蛋白质功能上重要的非谐运动，我们进行了羧基肌红蛋白（MbCO）动力学模拟，在此过程中禁止二面角转变。在三种水合水平以及100至400 K温度范围内模拟的扭转受限和不受限蛋白质动力学的比较表明，水合作用通过促进不需要二面角转变的集体非谐运动来“催化”蛋白质迁移率。当禁止二面角转变时，脱水的MbCO在很好的近似下仅表现出谐性波动，而水合的MbCO则表现出谐性和非谐运动。在扭转受限的水合系统中，螺旋质心的波动也保持高度非谐性。对于分别由350和3830个水分子水合的MbCO，在禁止二面角转变后，300 K时的原子均方波动仅分别降低了28%和10%。
