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Ultrafast pore-loop dynamics in a AAA+ machine point to a Brownian-ratchet mechanism for protein translocation
AAA+ ring–shaped machines, such as the disaggregation machines ClpB and Hsp104, mediate ATP-driven substrate translocation through their central channel by a set of pore loops. Recent structural studies have suggested a universal hand-over-hand translocation mechanism with slow and rigid subunit mot...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Association for the Advancement of Science
2021
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8442866/ https://www.ncbi.nlm.nih.gov/pubmed/34516899 http://dx.doi.org/10.1126/sciadv.abg4674 |
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author | Mazal, Hisham Iljina, Marija Riven, Inbal Haran, Gilad |
author_facet | Mazal, Hisham Iljina, Marija Riven, Inbal Haran, Gilad |
author_sort | Mazal, Hisham |
collection | PubMed |
description | AAA+ ring–shaped machines, such as the disaggregation machines ClpB and Hsp104, mediate ATP-driven substrate translocation through their central channel by a set of pore loops. Recent structural studies have suggested a universal hand-over-hand translocation mechanism with slow and rigid subunit motions. However, functional and biophysical studies are in discord with this model. Here, we directly measure the real-time dynamics of the pore loops of ClpB during substrate threading, using single-molecule FRET spectroscopy. All pore loops undergo large-amplitude fluctuations on the microsecond time scale and change their conformation upon interaction with substrate proteins in an ATP-dependent manner. Conformational dynamics of two of the pore loops strongly correlate with disaggregation activity, suggesting that they are the main contributors to substrate pulling. This set of findings is rationalized in terms of an ultrafast Brownian-ratchet translocation mechanism, which likely acts in parallel to the much slower hand-over-hand process in ClpB and other AAA+ machines. |
format | Online Article Text |
id | pubmed-8442866 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2021 |
publisher | American Association for the Advancement of Science |
record_format | MEDLINE/PubMed |
spelling | pubmed-84428662021-09-24 Ultrafast pore-loop dynamics in a AAA+ machine point to a Brownian-ratchet mechanism for protein translocation Mazal, Hisham Iljina, Marija Riven, Inbal Haran, Gilad Sci Adv Physical and Materials Sciences AAA+ ring–shaped machines, such as the disaggregation machines ClpB and Hsp104, mediate ATP-driven substrate translocation through their central channel by a set of pore loops. Recent structural studies have suggested a universal hand-over-hand translocation mechanism with slow and rigid subunit motions. However, functional and biophysical studies are in discord with this model. Here, we directly measure the real-time dynamics of the pore loops of ClpB during substrate threading, using single-molecule FRET spectroscopy. All pore loops undergo large-amplitude fluctuations on the microsecond time scale and change their conformation upon interaction with substrate proteins in an ATP-dependent manner. Conformational dynamics of two of the pore loops strongly correlate with disaggregation activity, suggesting that they are the main contributors to substrate pulling. This set of findings is rationalized in terms of an ultrafast Brownian-ratchet translocation mechanism, which likely acts in parallel to the much slower hand-over-hand process in ClpB and other AAA+ machines. American Association for the Advancement of Science 2021-09-03 /pmc/articles/PMC8442866/ /pubmed/34516899 http://dx.doi.org/10.1126/sciadv.abg4674 Text en Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY). https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution license (https://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Physical and Materials Sciences Mazal, Hisham Iljina, Marija Riven, Inbal Haran, Gilad Ultrafast pore-loop dynamics in a AAA+ machine point to a Brownian-ratchet mechanism for protein translocation |
title | Ultrafast pore-loop dynamics in a AAA+ machine point to a Brownian-ratchet mechanism for protein translocation |
title_full | Ultrafast pore-loop dynamics in a AAA+ machine point to a Brownian-ratchet mechanism for protein translocation |
title_fullStr | Ultrafast pore-loop dynamics in a AAA+ machine point to a Brownian-ratchet mechanism for protein translocation |
title_full_unstemmed | Ultrafast pore-loop dynamics in a AAA+ machine point to a Brownian-ratchet mechanism for protein translocation |
title_short | Ultrafast pore-loop dynamics in a AAA+ machine point to a Brownian-ratchet mechanism for protein translocation |
title_sort | ultrafast pore-loop dynamics in a aaa+ machine point to a brownian-ratchet mechanism for protein translocation |
topic | Physical and Materials Sciences |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8442866/ https://www.ncbi.nlm.nih.gov/pubmed/34516899 http://dx.doi.org/10.1126/sciadv.abg4674 |
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