期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2003
卷号：100
期号：26
页码：15486-15491
DOI：10.1073/pnas.2136623100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Here, we describe the folding/unfolding kinetics of 3D, a small designed three-helix bundle. Both IR temperature jump and ultrafast fluorescence mixing methods reveal a single-exponential process consistent with a minimal folding time of 3.2 {+/-} 1.2 {micro}s (at {approx}50{degrees}C), indicating that a protein can fold on the 1- to 5-{micro}s time scale. Furthermore, the single-exponential nature of the relaxation indicates that the prefactor for transition state (TS)-folding models is probably [≥]1 ({micro}s)-1 for a protein of this size and topology. Molecular dynamics simulations and IR spectroscopy provide a molecular rationale for the rapid, single-exponential folding of this protein. 3D shows a significant bias toward local helical structure in the thermally denatured state. The molecular dynamics-simulated TS ensemble is highly heterogeneous and dynamic, allowing access to the TS via multiple pathways.
