Sansom M S, Kerr I D
Laboratory of Molecular Biophysics, University of Oxford, United Kingdom.
Biophys J. 1995 Oct;69(4):1334-43. doi: 10.1016/S0006-3495(95)80000-7.
Transmembrane beta-barrels, first observed in bacterial porins, are possible models for a number of membrane channels. Restrained molecular dynamics simulations based on idealized C alpha beta templates have been used to generate models of such beta-barrels. Model beta-barrels have been analyzed in terms of their conformational, energetic, and pore properties. Model beta-barrels formed by N = 4, 8, 12 and 16 anti-parallel Ala10 strands have been developed. For each N, beta-barrels with shear numbers S = N to 2N have been modeled. In all beta-barrel models the constituent beta-strands adopt a pronounced right-handed twist. Interstrand interactions are of approximately equal stability for all models with N > or = 8, whereas such interactions are weaker for the N = 4 beta-barrels. In N = 4 beta-barrels the pore is too narrow (minimum radius approximately 0.6 A) to allow ion permeation. For N > or = 8, the pore radius depends on both N and S; for a given value of N an increase in S from N to 2N is predicted to result in an approximately threefold increase in pore conductance. Calculated maximal conductances for the beta-barrel models are compared with experimental values for porins and for K+ channels.
跨膜β桶结构最早在细菌孔蛋白中被观察到，它可能是多种膜通道的模型。基于理想化的Cαβ模板进行的受限分子动力学模拟已被用于生成此类β桶的模型。已从构象、能量和孔特性方面对模型β桶进行了分析。已经构建了由N = 4、8、12和16条反平行Ala10链形成的模型β桶。对于每个N，已经对剪切数S = N到2N的β桶进行了建模。在所有β桶模型中，组成β链都呈现出明显的右手扭曲。对于所有N≥8的模型，链间相互作用的稳定性大致相等，而对于N = 4的β桶，这种相互作用较弱。在N = 4的β桶中，孔太窄（最小半径约为0.6埃），无法允许离子渗透。对于N≥8，孔半径取决于N和S；对于给定的N值，预测S从N增加到2N会导致孔电导增加约三倍。将β桶模型的计算最大电导率与孔蛋白和钾通道的实验值进行了比较。
