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Substrate specificity and ion coupling in the Na+/betaine symporter BetP

Perez, Camilo and Koshy, Caroline and Ressl, Susanne and Nicklisch, Sascha and Krämer, Reinhard and Ziegler, Christine. (2011) Substrate specificity and ion coupling in the Na+/betaine symporter BetP. The EMBO Journal, 30 (7). pp. 1221-1229.

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Official URL: http://edoc.unibas.ch/56049/

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Abstract

BetP is an Na(+)-coupled betaine-specific transporter of the betaine-choline-carnitine (BCC) transporter family involved in the response to hyperosmotic stress. The crystal structure of BetP revealed an overall fold of two inverted structurally related repeats (LeuT-fold) that BetP shares with other sequence-unrelated Na(+)-coupled symporters. Numerous structures of LeuT-fold transporters in distinct conformational states have contributed substantially to our understanding of the alternating access mechanism of transport. Nevertheless, coupling of substrate and co-transported ion fluxes has not been structurally corroborated to the same extent. We converted BetP by a single-point mutation--glycine to aspartate--into an H(+)-coupled choline-specific transporter and solved the crystal structure of this mutant in complex with choline. The structure of BetP-G153D demonstrates a new inward-facing open conformation for BetP. Choline binding to a location close to the second, low-affinity sodium-binding site (Na2) of LeuT-fold transporters is facilitated by the introduced aspartate. Our data confirm the importance of a cation-binding site in BetP, playing a key role in a proposed molecular mechanism of Na(+) and H(+) coupling in BCC transporters.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Structural Biology & Biophysics
UniBasel Contributors:Perez, Camilo
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Nature Publishing Group
ISSN:0261-4189
e-ISSN:1460-2075
Note:Publication type according to Uni Basel Research Database: Journal article
Identification Number:
Last Modified:30 Nov 2017 10:02
Deposited On:30 Nov 2017 10:02

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