Conformational Dynamics of a Membrane Transport Protein Probed by HDX and Covalent Labeling: The Glycerol Facilitator

摘要

Studies on the dynamics and function of membrane proteins continue to be a challenge for most analytical techniques. Here, the glycerol facilitator (GF) was investigated using hydrogen/ deuterium exchange (HDX) and pulsed oxidative labeling coupled with ESI-MS. GF has a homo-tetrameric structure. Each of the subunits forms a single transmembrane channel that selectively transports water and glycerol. HDX monitors the conformational dynamics of the backbone, while oxidative labeling reports on side chain solvent-accessibility. We find that the mobile nature of the half-helix TM7 ensures that the diffusion of guest molecules through the channel is both fast and selective. The current work highlights the complementary nature of HDX, covalent labeling, and X-ray crystallography for the characterization of membrane proteins.