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Backstepping Mechanism of Kinesin-1

Kinesin-1 is an ATP-driven molecular motor that transports cellular cargo along microtubules. At low loads, kinesin-1 almost always steps forward, toward microtubule plus ends, but at higher loads, it can also step backward. Backsteps are usually 8 nm but can be larger. These larger backward events...

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Detalles Bibliográficos
Autores principales: Toleikis, Algirdas, Carter, Nicholas J., Cross, Robert A.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Biophysical Society 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7732724/
https://www.ncbi.nlm.nih.gov/pubmed/33091340
http://dx.doi.org/10.1016/j.bpj.2020.09.034
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author Toleikis, Algirdas
Carter, Nicholas J.
Cross, Robert A.
author_facet Toleikis, Algirdas
Carter, Nicholas J.
Cross, Robert A.
author_sort Toleikis, Algirdas
collection PubMed
description Kinesin-1 is an ATP-driven molecular motor that transports cellular cargo along microtubules. At low loads, kinesin-1 almost always steps forward, toward microtubule plus ends, but at higher loads, it can also step backward. Backsteps are usually 8 nm but can be larger. These larger backward events of 16 nm, 24 nm, or more are thought to be slips rather than steps because they are too fast to consist of multiple, tightly coupled 8-nm steps. Here, we propose that not only these larger backsteps, but all kinesin-1 backsteps, are slips. We show first that kinesin waits before forward steps for less time than before backsteps and detachments; second, we show that kinesin waits for the same amount of time before backsteps and detachments; and third, we show that by varying the microtubule type, we can change the ratio of backsteps to detachments without affecting forward stepping. Our findings indicate that backsteps and detachments originate from the same state and that this state arises later in the mechanochemical cycle than the state that gives rise to forward steps. To explain our data, we propose that, in each cycle of ATP turnover, forward kinesin steps can only occur before Pi release, whereas backslips and detachments can only occur after Pi release. In the scheme we propose, Pi release gates access to a weak binding K⋅ADP-K⋅ADP state that can slip back along the microtubule, re-engage, release ADP, and try again to take an ATP-driven forward step. We predict that this rescued detachment pathway is key to maintaining kinesin processivity under load.
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spelling pubmed-77327242021-11-17 Backstepping Mechanism of Kinesin-1 Toleikis, Algirdas Carter, Nicholas J. Cross, Robert A. Biophys J Articles Kinesin-1 is an ATP-driven molecular motor that transports cellular cargo along microtubules. At low loads, kinesin-1 almost always steps forward, toward microtubule plus ends, but at higher loads, it can also step backward. Backsteps are usually 8 nm but can be larger. These larger backward events of 16 nm, 24 nm, or more are thought to be slips rather than steps because they are too fast to consist of multiple, tightly coupled 8-nm steps. Here, we propose that not only these larger backsteps, but all kinesin-1 backsteps, are slips. We show first that kinesin waits before forward steps for less time than before backsteps and detachments; second, we show that kinesin waits for the same amount of time before backsteps and detachments; and third, we show that by varying the microtubule type, we can change the ratio of backsteps to detachments without affecting forward stepping. Our findings indicate that backsteps and detachments originate from the same state and that this state arises later in the mechanochemical cycle than the state that gives rise to forward steps. To explain our data, we propose that, in each cycle of ATP turnover, forward kinesin steps can only occur before Pi release, whereas backslips and detachments can only occur after Pi release. In the scheme we propose, Pi release gates access to a weak binding K⋅ADP-K⋅ADP state that can slip back along the microtubule, re-engage, release ADP, and try again to take an ATP-driven forward step. We predict that this rescued detachment pathway is key to maintaining kinesin processivity under load. The Biophysical Society 2020-11-17 2020-10-06 /pmc/articles/PMC7732724/ /pubmed/33091340 http://dx.doi.org/10.1016/j.bpj.2020.09.034 Text en © 2020 Biophysical Society. http://creativecommons.org/licenses/by/4.0/ This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Articles
Toleikis, Algirdas
Carter, Nicholas J.
Cross, Robert A.
Backstepping Mechanism of Kinesin-1
title Backstepping Mechanism of Kinesin-1
title_full Backstepping Mechanism of Kinesin-1
title_fullStr Backstepping Mechanism of Kinesin-1
title_full_unstemmed Backstepping Mechanism of Kinesin-1
title_short Backstepping Mechanism of Kinesin-1
title_sort backstepping mechanism of kinesin-1
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7732724/
https://www.ncbi.nlm.nih.gov/pubmed/33091340
http://dx.doi.org/10.1016/j.bpj.2020.09.034
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