Moran L B, Schneider J P, Kentsis A, Reddy G A, Sosnick T R
Department of Biochemistry and Molecular Biology, University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA.
Proc Natl Acad Sci U S A. 1999 Sep 14;96(19):10699-704. doi: 10.1073/pnas.96.19.10699.
We have investigated the folding behavior of dimeric and covalently crosslinked versions of the 33-residue alpha-helical GCN4-p1 coiled coil derived from the leucine zipper region of the transcriptional activator GCN4. The effects of multisite substitutions indicate that folding occurs along multiple routes with nucleation sites located throughout the protein. The similarity in activation energies of the different routes together with an analysis of intrinsic helical propensities indicate that minimal helix is present before a productive collision of the two chains. However, approximately one-third to one-half of the total helical structure is formed in the postcollision transition state ensemble. For the crosslinked, monomeric version, folding occurs along a single robust pathway. Here, the region nearest the crosslink, with the least helical propensity, is structured in the transition state whereas the region farthest from the tether, with the most propensity, is completely unstructured. Hence, the existence of transition state heterogeneity and the selection of folding routes critically depend on chain topology.
我们研究了源自转录激活因子GCN4亮氨酸拉链区域的33个残基的α-螺旋GCN4-p1卷曲螺旋的二聚体和共价交联形式的折叠行为。多位点取代的影响表明，折叠沿着多条途径发生，成核位点遍布整个蛋白质。不同途径的活化能相似性以及对内在螺旋倾向的分析表明，在两条链发生有效碰撞之前，存在最小螺旋。然而，在碰撞后过渡态集合中形成了约三分之一到二分之一的总螺旋结构。对于交联的单体形式，折叠沿着单一稳健途径发生。在这里，最靠近交联点、螺旋倾向最小的区域在过渡态中形成结构，而离系链最远、螺旋倾向最大的区域则完全无结构。因此，过渡态异质性的存在和折叠途径的选择关键取决于链拓扑结构。
