期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 104, 期 44, 页码 17400-17405出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0705605104
关键词
fluorescence correlation spectroscopy; molecular ruler; prolyl isomerization; biopolymer; Forster resonance energy transfer
Polyprolines are well known for adopting a regular polyproline type II helix in aqueous solution, rendering them a popular standard as molecular ruler in structural molecular biology. However, single-molecule spectroscopy studies based on Forster resonance energy transfer (FRET) have revealed deviations of experimentally observed end-to-end distances of polyprolines from theoretical predictions, and it was proposed that the discrepancy resulted from dynamic flexibility of the polyproline helix. Here, we probe end-to-end distances and conformational dynamics Of Poly-L-prolines with 1-10 residues using fluorescence quenching by photoinduced-electron transfer (PET). A single fluorophore and a tryptophan residue, introduced at the termini of polyproline peptides, serve as sensitive probes for distance changes on the subnanometer length scale. Using a combination of ensemble fluorescence and fluorescence correlation spectroscopy, we demonstrate that polyproline samples exhibit static structural heterogeneity with subpopulations of distinct end-to-end distances that do not interconvert on time scales from nano- to milliseconds. By observing prolyl isomerization through changes in PET quenching interactions, we provide experimental evidence that the observed heterogeneity can be explained by interspersed cis isomers. Computer simulations elucidate the influence of trans/cis isomerization on polyproline structures in terms of end-to-end distance and provide a structural justification for the experimentally observed effects. Our results demonstrate that structural heterogeneity inherent in polyprolines, which to date are commonly applied as a molecular ruler, disqualifies them as appropriate tool for an accurate determination of absolute distances at a molecular scale.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据