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Locating an extracellular K+-dependent interaction site that modulates betaine-binding of the Na+-coupled betaine symporter BetP

Ge, Lin and Perez, Camilo and Waclawska, Izabela and Ziegler, Christine and Muller, Daniel J.. (2011) Locating an extracellular K+-dependent interaction site that modulates betaine-binding of the Na+-coupled betaine symporter BetP. Proceedings of the National Academy of Sciences, 108 (43). E890-E898.

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Official URL: http://edoc.unibas.ch/56047/

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Abstract

BetP, a trimeric Na(+)-coupled betaine symporter, senses hyperosmotic stress via its cytoplasmic C-terminal domain and regulates transport activity in dependence of the cytoplasmic K(+)-concentration. This transport regulation of BetP depends on a sophisticated interaction network. Using single-molecule force spectroscopy we structurally localize and quantify these interactions changing on K(+)-dependent transport activation and substrate-binding. K(+) significantly strengthened all interactions, modulated lifetimes of functionally important structural regions, and increased the mechanical rigidity of the symporter. Substrate-binding could modulate, but not establish most of these K(+)-dependent interactions. A pronounced effect triggered by K(+) was observed at the periplasmic helical loop EH2. Tryptophan quenching experiments revealed that elevated K(+)-concentrations akin to those BetP encounters during hyperosmotic stress trigger the formation of a periplasmic second betaine-binding (S2) site, which was found to be at a similar position reported previously for the BetP homologue CaiT. In BetP, the presence of the S2 site strengthened the interaction between EH2, transmembrane α-helix 12 and the K(+)-sensing C-terminal domain resulting in a K(+)-dependent cooperative betaine-binding.
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:National Academy of Sciences
ISSN:0027-8424
e-ISSN:1091-6490
Note:Publication type according to Uni Basel Research Database: Journal article
Identification Number:
Last Modified:30 Nov 2017 09:58
Deposited On:30 Nov 2017 09:58

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