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The β Subunit of the Sec61 Complex Facilitates Cotranslational Protein Transport and Interacts with the Signal Peptidase during Translocation

The Sec61 complex is the central component of the protein translocation apparatus of the ER membrane. We have addressed the role of the β subunit (Sec61β) during cotranslational protein translocation. With a reconstituted system, we show that a Sec61 complex lacking Sec61β is essentially inactive wh...

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Detalles Bibliográficos
Autores principales: Kalies, Kai-Uwe, Rapoport, Tom A., Hartmann, Enno
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1998
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2132780/
https://www.ncbi.nlm.nih.gov/pubmed/9585408
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author Kalies, Kai-Uwe
Rapoport, Tom A.
Hartmann, Enno
author_facet Kalies, Kai-Uwe
Rapoport, Tom A.
Hartmann, Enno
author_sort Kalies, Kai-Uwe
collection PubMed
description The Sec61 complex is the central component of the protein translocation apparatus of the ER membrane. We have addressed the role of the β subunit (Sec61β) during cotranslational protein translocation. With a reconstituted system, we show that a Sec61 complex lacking Sec61β is essentially inactive when elongation and membrane targeting of a nascent chain occur at the same time. The translocation process is perturbed at a step where the nascent chain would be inserted into the translocation channel. However, if sufficient time is given for the interaction of the nascent polypeptide with the mutant Sec61 complex, translocation is almost normal. Thus Sec61β kinetically facilitates cotranslational translocation, but is not essential for it. Using chemical cross-linking we show that Sec61β not only interacts with subunits of the Sec61 complex but also with the 25-kD subunit of the signal peptidase complex (SPC25), thus demonstrating for the first time a tight interaction between the SPC and the Sec61 complex. Interestingly, the cross-links between Sec61β and SPC25 and between Sec61β and Sec61α depend on the presence of membrane-bound ribosomes, suggesting that these interactions are induced when translocation is initiated. We propose that the SPC is transiently recruited to the translocation site, thus enhancing its activity.
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spelling pubmed-21327802008-05-01 The β Subunit of the Sec61 Complex Facilitates Cotranslational Protein Transport and Interacts with the Signal Peptidase during Translocation Kalies, Kai-Uwe Rapoport, Tom A. Hartmann, Enno J Cell Biol Articles The Sec61 complex is the central component of the protein translocation apparatus of the ER membrane. We have addressed the role of the β subunit (Sec61β) during cotranslational protein translocation. With a reconstituted system, we show that a Sec61 complex lacking Sec61β is essentially inactive when elongation and membrane targeting of a nascent chain occur at the same time. The translocation process is perturbed at a step where the nascent chain would be inserted into the translocation channel. However, if sufficient time is given for the interaction of the nascent polypeptide with the mutant Sec61 complex, translocation is almost normal. Thus Sec61β kinetically facilitates cotranslational translocation, but is not essential for it. Using chemical cross-linking we show that Sec61β not only interacts with subunits of the Sec61 complex but also with the 25-kD subunit of the signal peptidase complex (SPC25), thus demonstrating for the first time a tight interaction between the SPC and the Sec61 complex. Interestingly, the cross-links between Sec61β and SPC25 and between Sec61β and Sec61α depend on the presence of membrane-bound ribosomes, suggesting that these interactions are induced when translocation is initiated. We propose that the SPC is transiently recruited to the translocation site, thus enhancing its activity. The Rockefeller University Press 1998-05-18 /pmc/articles/PMC2132780/ /pubmed/9585408 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Articles
Kalies, Kai-Uwe
Rapoport, Tom A.
Hartmann, Enno
The β Subunit of the Sec61 Complex Facilitates Cotranslational Protein Transport and Interacts with the Signal Peptidase during Translocation
title The β Subunit of the Sec61 Complex Facilitates Cotranslational Protein Transport and Interacts with the Signal Peptidase during Translocation
title_full The β Subunit of the Sec61 Complex Facilitates Cotranslational Protein Transport and Interacts with the Signal Peptidase during Translocation
title_fullStr The β Subunit of the Sec61 Complex Facilitates Cotranslational Protein Transport and Interacts with the Signal Peptidase during Translocation
title_full_unstemmed The β Subunit of the Sec61 Complex Facilitates Cotranslational Protein Transport and Interacts with the Signal Peptidase during Translocation
title_short The β Subunit of the Sec61 Complex Facilitates Cotranslational Protein Transport and Interacts with the Signal Peptidase during Translocation
title_sort β subunit of the sec61 complex facilitates cotranslational protein transport and interacts with the signal peptidase during translocation
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2132780/
https://www.ncbi.nlm.nih.gov/pubmed/9585408
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