蛋白质电子晶体学

Electron Crystallography of Proteins

把电子晶体学的概念和数学手段引入生物大分子结构研究是25年来结构分子生物学的一个重要发展。电子的高散射能力使得能从一层单胞厚度的大分子单晶收集结构数据,以研究可以生长成二维晶体的大分子的高分辨率三维结构,如膜蛋白。物体的电子显微像包含了其结构因子的振幅和相位信息,通过三维像重构可研究任何分子量大于500 KD的具有二十面体对称和螺旋对称的甚至无对称性的大分子或其集合体的三维结构。迄今,用电子晶体学方法已解出某些膜蛋白的近原子分辨率的结构并获得二十面体和螺旋对称的大分子或其集合体的大量结构信息。已经和正在发展的样品制备技术、高分辨成像仪器的利用、成像条件和数据收集方法的改进以及先进算法的发展,将有可能使蛋白质电子晶体学达到原子分辨率水平。近年来,我们在膜蛋白的二维晶体的生长、水溶性蛋白质薄晶体的生长及其结构分析以及大分子样品的低温电子显微术研究方面已取得可喜的进展。

During the past decade, an important advance in the structural molecular biology was that the concept and mathematical approach of crystallographic structure analysis were introduced to the electron microscopy in structural study of biological macromolecules, The very high scattering power of electron makes it possible to get sufficient signal from two-dimensional single-crystal specimens of biological macromolecules. The electron crystallography of proteins is suitable, therefore, for structural studies of the proteins such as the membrane proteins and some water-soluable proteins that grow into two-dimensional crystals under certain conditions. The structure of any biological macromolecules or molecular assembly with a size of>500 kDa can also be studied from their electron-micrographs by three-dimensional reconstruction because the images of the macromolecules contain both amplitude and phase information. So far, three-dimensional structures of some membrane proteins have solved at near atomic resolution and numerous structural information of other macromolecules or their assembly with icosahedral and helical symmetry or with asymmetry have been obtained by electron crystallography. Recently, we have made some progress on two-dimensional crystallization of several membrane proteins, structural analysis of thin protein crystals and cryoelectron microscopy of biological macromolecules.