BetP is critical for responses to hyperosmotic stress and cotransports Na+ and betaine.
•Hyperosmotic stress increases intracellular K+ concentrations promoting betaine binding.
•C-terminal K+ binding activates an allosteric relay to enhance betaine binding which was unknown.
•HDXMS reveals how K+ initiates the allosteric relay to transmembrane helices 3, 8, and 10.
•High resolution HDXMS betaine binding map reveals critical extrahelical H-bond.
AbstractThe transporter BetP in C. glutamicum is essential in maintaining bacterial cell viability during hyperosmotic stress and functions by co-transporting betaine and Na+ into bacterial cells. Hyperosmotic stress leads to increased intracellular K+ concentrations which in turn promotes betaine binding. While structural details of multiple end state conformations of BetP have provided high resolution snapshots, how K+ sensing by the C-terminal domain is allosterically relayed to the betaine binding site is not well understood. In this study, we describe conformational dynamics in solution of BetP using amide hydrogen/deuterium exchange mass spectrometry. These reveal how K+ alters conformation of the disordered C- and N-terminal domains to allosterically reconfigure transmembrane helices 3, 8, and 10 to enhance betaine interactions. A map of the betaine binding site, at near single amino acid resolution, reveals a critical extrahelical H-bond mediated by TM3 with betaine.
KeywordsBetP transporter
amphipols
allostery
hyperosmotic stress
View Abstract© 2022 Elsevier Ltd. All rights reserved.
留言 (0)