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Force Dependence of Proteins’ Transition State Position and the Bell–Evans Model

Single-molecule force spectroscopy has opened a new field of research in molecular biophysics and biochemistry. Pulling experiments on individual proteins permit us to monitor conformational transitions with high temporal resolution and measure their free energy landscape. The force–extension curves...

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Autores principales: Rico-Pasto, Marc, Zaltron, Annamaria, Ritort, Felix
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8617895/
https://www.ncbi.nlm.nih.gov/pubmed/34835787
http://dx.doi.org/10.3390/nano11113023
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author Rico-Pasto, Marc
Zaltron, Annamaria
Ritort, Felix
author_facet Rico-Pasto, Marc
Zaltron, Annamaria
Ritort, Felix
author_sort Rico-Pasto, Marc
collection PubMed
description Single-molecule force spectroscopy has opened a new field of research in molecular biophysics and biochemistry. Pulling experiments on individual proteins permit us to monitor conformational transitions with high temporal resolution and measure their free energy landscape. The force–extension curves of single proteins often present large hysteresis, with unfolding forces that are higher than refolding ones. Therefore, the high energy of the transition state (TS) in these molecules precludes kinetic rates measurements in equilibrium hopping experiments. In irreversible pulling experiments, force-dependent kinetic rates measurements show a systematic discrepancy between the sum of the folding and unfolding TS distances derived by the kinetic Bell–Evans model and the full molecular extension predicted by elastic models. Here, we show that this discrepancy originates from the force-induced movement of TS. Specifically, we investigate the highly kinetically stable protein barnase, using pulling experiments and the Bell–Evans model to characterize the position of its kinetic barrier. Experimental results show that while the TS stays at a roughly constant distance relative to the native state, it shifts with force relative to the unfolded state. Interestingly, a conversion of the protein extension into amino acid units shows that the TS position follows the Leffler–Hammond postulate: the higher the force, the lower the number of unzipped amino acids relative to the native state. The results are compared with the quasi-reversible unfolding–folding of a short DNA hairpin.
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spelling pubmed-86178952021-11-27 Force Dependence of Proteins’ Transition State Position and the Bell–Evans Model Rico-Pasto, Marc Zaltron, Annamaria Ritort, Felix Nanomaterials (Basel) Article Single-molecule force spectroscopy has opened a new field of research in molecular biophysics and biochemistry. Pulling experiments on individual proteins permit us to monitor conformational transitions with high temporal resolution and measure their free energy landscape. The force–extension curves of single proteins often present large hysteresis, with unfolding forces that are higher than refolding ones. Therefore, the high energy of the transition state (TS) in these molecules precludes kinetic rates measurements in equilibrium hopping experiments. In irreversible pulling experiments, force-dependent kinetic rates measurements show a systematic discrepancy between the sum of the folding and unfolding TS distances derived by the kinetic Bell–Evans model and the full molecular extension predicted by elastic models. Here, we show that this discrepancy originates from the force-induced movement of TS. Specifically, we investigate the highly kinetically stable protein barnase, using pulling experiments and the Bell–Evans model to characterize the position of its kinetic barrier. Experimental results show that while the TS stays at a roughly constant distance relative to the native state, it shifts with force relative to the unfolded state. Interestingly, a conversion of the protein extension into amino acid units shows that the TS position follows the Leffler–Hammond postulate: the higher the force, the lower the number of unzipped amino acids relative to the native state. The results are compared with the quasi-reversible unfolding–folding of a short DNA hairpin. MDPI 2021-11-11 /pmc/articles/PMC8617895/ /pubmed/34835787 http://dx.doi.org/10.3390/nano11113023 Text en © 2021 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Rico-Pasto, Marc
Zaltron, Annamaria
Ritort, Felix
Force Dependence of Proteins’ Transition State Position and the Bell–Evans Model
title Force Dependence of Proteins’ Transition State Position and the Bell–Evans Model
title_full Force Dependence of Proteins’ Transition State Position and the Bell–Evans Model
title_fullStr Force Dependence of Proteins’ Transition State Position and the Bell–Evans Model
title_full_unstemmed Force Dependence of Proteins’ Transition State Position and the Bell–Evans Model
title_short Force Dependence of Proteins’ Transition State Position and the Bell–Evans Model
title_sort force dependence of proteins’ transition state position and the bell–evans model
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8617895/
https://www.ncbi.nlm.nih.gov/pubmed/34835787
http://dx.doi.org/10.3390/nano11113023
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