Fersht A R
Cambridge Centre for Protein Engineering, Department of Chemistry, University of Cambridge, U.K.
Philos Trans R Soc Lond B Biol Sci. 1995 Apr 29;348(1323):11-5. doi: 10.1098/rstb.1995.0040.
The structures of all the intermediates and transition states, from the unfolded state to the native structure, are being determined at the level of individual residues in the folding pathways of barnase and chymotrypsin inhibitor 2 (CI2), using a combination of protein engineering and nuclear magnetic resonance methods. Barnase appears to refold according to a classical framework model in which elements of secondary structure are flickeringly present in the denatured state, consolidate as the reaction proceeds and, when nearly fully formed, dock in the rate-determining step. Unlike barnase, CI2 folds without a kinetically significant folding intermediate. The transition state for its formation has no fully formed elements of secondary structure, and the transition state is like an expanded form of the native structure. CI2 probably represents the folding of an individual domain in a larger protein, whereas barnase represents the folding of a multi-domain protein. The protein engineering methods are being extended to map the pathway in the presence of molecular chaperones. There are parallels between the folding of barnase when bound to GroEL and in solution.
从去折叠状态到天然结构，所有中间体和过渡态的结构正在通过蛋白质工程和核磁共振方法相结合，在核糖核酸酶（barnase）和胰凝乳蛋白酶抑制剂2（CI2）折叠途径中的单个残基水平上进行测定。核糖核酸酶似乎按照经典的框架模型重新折叠，在该模型中，二级结构元件在变性状态下短暂存在，随着反应进行而巩固，并且在几乎完全形成时，在速率决定步骤中对接。与核糖核酸酶不同，CI2折叠时没有动力学上显著的折叠中间体。其形成的过渡态没有完全形成的二级结构元件，并且过渡态类似于天然结构的扩展形式。CI2可能代表较大蛋白质中单个结构域的折叠，而核糖核酸酶代表多结构域蛋白质的折叠。蛋白质工程方法正在扩展以绘制在分子伴侣存在下的途径。与GroEL结合时和在溶液中的核糖核酸酶折叠之间存在相似之处。
