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

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 loo

SUBMITTER: Ge L 

PROVIDER: S-EPMC3203757 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature