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Published October 25, 2016 | Supplemental Material + Published
Journal Article Open

Theory of single-molecule controlled rotation experiments, predictions, tests, and comparison with stalling experiments in F₁-ATPase

Abstract

A recently proposed chemomechanical group transfer theory of rotary biomolecular motors is applied to treat single-molecule controlled rotation experiments. In these experiments, single-molecule fluorescence is used to measure the binding and release rate constants of nucleotides by monitoring the occupancy of binding sites. It is shown how missed events of nucleotide binding and release in these experiments can be corrected using theory, with F1-ATP synthase as an example. The missed events are significant when the reverse rate is very fast. Using the theory the actual rate constants in the controlled rotation experiments and the corrections are predicted from independent data, including other single-molecule rotation and ensemble biochemical experiments. The effective torsional elastic constant is found to depend on the binding/releasing nucleotide, and it is smaller for ADP than for ATP. There is a good agreement, with no adjustable parameters, between the theoretical and experimental results of controlled rotation experiments and stalling experiments, for the range of angles where the data overlap. This agreement is perhaps all the more surprising because it occurs even though the binding and release of fluorescent nucleotides is monitored at single-site occupancy concentrations, whereas the stalling and free rotation experiments have multiple-site occupancy.

Additional Information

© 2016 National Academy of Sciences. Contributed by Rudolph A. Marcus, August 26, 2016 (sent for review July 15, 2016; reviewed by Attila Szabo and Arieh Warshel). Published online before print October 10, 2016, doi: 10.1073/pnas.1611601113 We thank Drs. Imre Derényi and Kengo Adachi for helpful discussions and comments and the reviewers for useful suggestions. This work was supported by the Office of the Naval Research, the Army Research Office, and the James W. Glanville Foundation. Author contributions: S.V.-K. and R.A.M. designed research, performed research, analyzed data, and wrote the paper. Reviewers: A.S., National Institutes of Health; and A.W., University of Southern California. The authors declare no conflict of interest. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1611601113/-/DCSupplemental.

Attached Files

Published - volkan-kacso-marcus-2016-theory-of-single-molecule-controlled-rotation-experiments-predictions-tests-and-comparison.pdf

Supplemental Material - pnas_201611601si.pdf

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pnas_201611601si.pdf

Additional details

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September 28, 2023
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October 24, 2023