Cao Y, Musah R A, Wilcox S K, Goodin D B, McRee D E
Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Protein Sci. 1998 Jan;7(1):72-8. doi: 10.1002/pro.5560070107.
A large-scale movement between "closed" and "open" conformations of a protein loop was observed directly with protein crystallography by trapping individual conformers through binding of an exogenous ligand and characterization with solution kinetics. The buried indole ring of Trp191 in cytochrome c peroxidase (CCP) was displaced by exogenous ligands, causing a conformational change of loop Pro190-Asn195 and exposing Trp191 to the protein surface. Kinetic measurements are consistent with a two-step binding mechanism in which the rate-limiting step is a transition of the protein to the open state, which then binds the ligand. This large-scale conformational change of a functionally important region of CCP is independent of ligand and indicates that about 4% of the wild-type protein is in the open form in solution at any given time.
通过结合外源性配体捕获单个构象异构体，并利用溶液动力学进行表征，利用蛋白质晶体学直接观察到蛋白质环在“封闭”和“开放”构象之间的大规模运动。细胞色素c过氧化物酶（CCP）中Trp191的埋藏吲哚环被外源性配体取代，导致Pro190-Asn195环的构象变化，并使Trp191暴露于蛋白质表面。动力学测量结果与两步结合机制一致，其中限速步骤是蛋白质向开放状态的转变，然后与配体结合。CCP功能重要区域的这种大规模构象变化与配体无关，表明在任何给定时间，约4%的野生型蛋白质在溶液中呈开放形式。
