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

Ge, L., Perez, C., Waclawska, I., Ziegler, C., & Muller, D. 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 of the United States of America, 108(43), E890-E898. doi:10.1073/pnas.1109597108.

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 Creators:
Ge, Lin1, Author
Perez, Camilo2, Author           
Waclawska, Izabela2, Author           
Ziegler, Christine2, Author           
Muller, Daniel J.1, Author
Affiliations:
1Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule Zurich, 4058 Basel, Switzerland, ou_persistent22              
2Department of Structural Biology, Max Planck Institute of Biophysics, Max Planck Society, ou_2068291              

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Free keywords: atomic force microscopy; energy landscape; membrane transporter; osmoregulation; secondary substrate-binding site
 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.

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Language(s): deu - German
 Dates: 2011-06-142011-09-092011-10-102011-10-25
 Publication Status: Published in print
 Pages: 9
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1073/pnas.1109597108
PMID: 21987793
PMC: PMC3203757
 Degree: -

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Title: Proceedings of the National Academy of Sciences of the United States of America
  Other : PNAS
  Other : Proceedings of the National Academy of Sciences of the USA
  Abbreviation : Proc. Natl. Acad. Sci. U. S. A.
Source Genre: Journal
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Publ. Info: Washington, D.C. : National Academy of Sciences
Pages: - Volume / Issue: 108 (43) Sequence Number: - Start / End Page: E890 - E898 Identifier: ISSN: 0027-8424
CoNE: https://pure.mpg.de/cone/journals/resource/954925427230