Frauenfelder Hans, Chen Guo, Berendzen Joel, Fenimore Paul W, Jansson Helén, McMahon Benjamin H, Stroe Izabela R, Swenson Jan, Young Robert D
Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
Proc Natl Acad Sci U S A. 2009 Mar 31;106(13):5129-34. doi: 10.1073/pnas.0900336106. Epub 2009 Feb 27.
Protein functions require conformational motions. We show here that the dominant conformational motions are slaved by the hydration shell and the bulk solvent. The protein contributes the structure necessary for function. We formulate a model that is based on experiments, insights from the physics of glass-forming liquids, and the concepts of a hierarchically organized energy landscape. To explore the effect of external fluctuations on protein dynamics, we measure the fluctuations in the bulk solvent and the hydration shell with broadband dielectric spectroscopy and compare them with internal fluctuations measured with the Mössbauer effect and neutron scattering. The result is clear. Large-scale protein motions are slaved to the fluctuations in the bulk solvent. They are controlled by the solvent viscosity, and are absent in a solid environment. Internal protein motions are slaved to the beta fluctuations of the hydration shell, are controlled by hydration, and are absent in a dehydrated protein. The model quantitatively predicts the rapid increase of the mean-square displacement above approximately 200 K, shows that the external beta fluctuations determine the temperature- and time-dependence of the passage of carbon monoxide through myoglobin, and explains the nonexponential time dependence of the protein relaxation after photodissociation.
蛋白质功能需要构象运动。我们在此表明，主要的构象运动受水化层和主体溶剂的支配。蛋白质提供功能所需的结构。我们构建了一个基于实验、玻璃形成液体物理学的见解以及层次组织的能量景观概念的模型。为了探究外部涨落对蛋白质动力学的影响，我们用宽带介电谱测量主体溶剂和水化层中的涨落，并将其与用穆斯堡尔效应和中子散射测量的内部涨落进行比较。结果很明显。大规模的蛋白质运动受主体溶剂涨落的支配。它们受溶剂粘度控制，在固体环境中不存在。蛋白质内部运动受水化层的β涨落支配，受水化作用控制，在脱水蛋白质中不存在。该模型定量预测了均方位移在约200 K以上的快速增加，表明外部β涨落决定了一氧化碳通过肌红蛋白的温度和时间依赖性，并解释了光解离后蛋白质弛豫的非指数时间依赖性。
