Effects of topology and excluded volume on protein denatured state conformational properties.
Effects of topology and excluded volume on protein denatured state conformational properties.
复制标题
拓扑和排除体积对蛋白质变性状态构象特性的影响。
DOI：
10.1021/bi0259249
复制
发表时间：
2002
期刊：
影响因子：
2.9
通讯作者：
Bowler,BruceE
中科院分区：
文献类型：
--
作者：
Smith,ChristopherR;Mateljevic,Natasa;Bowler,BruceE
The conformational constraints on protein denatured states are of prime importance in modulating early events in protein folding. Although structural studies have demonstrated residual structure in protein denatured states, much remains poorly understood with regard to the conformational properties of this state. Here, we investigate topological effects on loop formation probabilities in denatured iso-1-cytochromecby comparing histidine−heme binding affinities for histidines on the N- versus the C-terminal side of the heme. For histidines N-terminal to the heme (preceding cysteine 14), the polypeptide emerges from the edge of the heme and must simply fold over to bind to the heme. For histidines C-terminal to the heme (following histidine 18), the polypeptide emerges from the back side of the heme and must wrap around the heme for the histidine to bind to the heme. Thus, the steric constraints on this wrap-around topology are expected to be much more demanding than for the heme-edge topology of the N-terminal histidines. Evaluation of loop formation probabilities in 3 M guanidine hydrochloride, conditions that fully denature the variants studied, demonstrates that N-terminal histidine−heme loop formation is 10−25-fold more favorable than C-terminal histidine−heme loop formation, for similar loop sizes. A two-dimensional square lattice model indicates that excluded volume is important in this topological preference. These data provide direct evidence that denatured state topology affects contact probability, and thus probable folding pathways, in a disordered protein.
