期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 111, 期 49, 页码 17492-17497出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1419276111
关键词
cryo-electron microscopy; elongation cycle; manifold embedding; nanomachines; translation
资金
- US Department of Energy, Office of Science, Basic Energy Sciences [DE-FG02-09ER16114]
- Howard Hughes Medical Institute and National Institutes of Health [R01 GM29169, GM55440]
- National Science Foundation MCB [1157906]
- US National Science Foundation [STC 1231306]
- Div Of Molecular and Cellular Bioscience
- Direct For Biological Sciences [1157906] Funding Source: National Science Foundation
A Brownian machine, a tiny device buffeted by the random motions of molecules in the environment, is capable of exploiting these thermal motions for many of the conformational changes in its work cycle. Such machines are now thought to be ubiquitous, with the ribosome, a molecular machine responsible for protein synthesis, increasingly regarded as prototypical. Here we present a new analytical approach capable of determining the free-energy landscape and the continuous trajectories of molecular machines from a large number of snapshots obtained by cryogenic electron microscopy. We demonstrate this approach in the context of experimental cryogenic electron microscope images of a large ensemble of nontranslating ribosomes purified from yeast cells. The free-energy landscape is seen to contain a closed path of low energy, along which the ribosome exhibits conformational changes known to be associated with the elongation cycle. Our approach allows model-free quantitative analysis of the degrees of freedom and the energy landscape underlying continuous conformational changes in nanomachines, including those important for biological function.
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