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A Conformational Shift in the Dissociated Cholera Toxin A1 Subunit Prevents Reassembly of the Cholera Holotoxin

Cholera toxin (CT) consists of a catalytic A1 subunit, an A2 linker, and a homopentameric cell-binding B subunit. The intact holotoxin moves by vesicle carriers from the cell surface to the endoplasmic reticulum (ER) where CTA1 is released from the rest of the toxin. The dissociated CTA1 subunit the...

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Autores principales: Taylor, Michael, Curtis, David, Teter, Ken
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516936/
https://www.ncbi.nlm.nih.gov/pubmed/26266549
http://dx.doi.org/10.3390/toxins7072674
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author Taylor, Michael
Curtis, David
Teter, Ken
author_facet Taylor, Michael
Curtis, David
Teter, Ken
author_sort Taylor, Michael
collection PubMed
description Cholera toxin (CT) consists of a catalytic A1 subunit, an A2 linker, and a homopentameric cell-binding B subunit. The intact holotoxin moves by vesicle carriers from the cell surface to the endoplasmic reticulum (ER) where CTA1 is released from the rest of the toxin. The dissociated CTA1 subunit then shifts to an unfolded conformation, which triggers its export to the cytosol by a process involving the quality control system of ER-associated degradation (ERAD). We hypothesized that the unfolding of dissociated CTA1 would prevent its non-productive reassociation with CTA2/CTB(5). To test this prediction, we monitored the real-time reassociation of CTA1 with CTA2/CTB(5) by surface plasmon resonance. Folded but not disordered CTA1 could interact with CTA2/CTB(5) to form a stable, functional holotoxin. Our data, thus, identified another role for the intrinsic instability of the isolated CTA1 polypeptide in host-toxin interactions: in addition to activating the ERAD translocation mechanism, the spontaneous unfolding of free CTA1 at 37 °C prevents the non-productive reassembly of a CT holotoxin in the ER.
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spelling pubmed-45169362015-07-28 A Conformational Shift in the Dissociated Cholera Toxin A1 Subunit Prevents Reassembly of the Cholera Holotoxin Taylor, Michael Curtis, David Teter, Ken Toxins (Basel) Article Cholera toxin (CT) consists of a catalytic A1 subunit, an A2 linker, and a homopentameric cell-binding B subunit. The intact holotoxin moves by vesicle carriers from the cell surface to the endoplasmic reticulum (ER) where CTA1 is released from the rest of the toxin. The dissociated CTA1 subunit then shifts to an unfolded conformation, which triggers its export to the cytosol by a process involving the quality control system of ER-associated degradation (ERAD). We hypothesized that the unfolding of dissociated CTA1 would prevent its non-productive reassociation with CTA2/CTB(5). To test this prediction, we monitored the real-time reassociation of CTA1 with CTA2/CTB(5) by surface plasmon resonance. Folded but not disordered CTA1 could interact with CTA2/CTB(5) to form a stable, functional holotoxin. Our data, thus, identified another role for the intrinsic instability of the isolated CTA1 polypeptide in host-toxin interactions: in addition to activating the ERAD translocation mechanism, the spontaneous unfolding of free CTA1 at 37 °C prevents the non-productive reassembly of a CT holotoxin in the ER. MDPI 2015-07-20 /pmc/articles/PMC4516936/ /pubmed/26266549 http://dx.doi.org/10.3390/toxins7072674 Text en © 2015 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Taylor, Michael
Curtis, David
Teter, Ken
A Conformational Shift in the Dissociated Cholera Toxin A1 Subunit Prevents Reassembly of the Cholera Holotoxin
title A Conformational Shift in the Dissociated Cholera Toxin A1 Subunit Prevents Reassembly of the Cholera Holotoxin
title_full A Conformational Shift in the Dissociated Cholera Toxin A1 Subunit Prevents Reassembly of the Cholera Holotoxin
title_fullStr A Conformational Shift in the Dissociated Cholera Toxin A1 Subunit Prevents Reassembly of the Cholera Holotoxin
title_full_unstemmed A Conformational Shift in the Dissociated Cholera Toxin A1 Subunit Prevents Reassembly of the Cholera Holotoxin
title_short A Conformational Shift in the Dissociated Cholera Toxin A1 Subunit Prevents Reassembly of the Cholera Holotoxin
title_sort conformational shift in the dissociated cholera toxin a1 subunit prevents reassembly of the cholera holotoxin
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516936/
https://www.ncbi.nlm.nih.gov/pubmed/26266549
http://dx.doi.org/10.3390/toxins7072674
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