Conformation-dependent diffusion properties of a transmembrane protein.

Abstract

Fundamental cell physiology originates from conformational changes and diffusion dynamics of membrane proteins. However, studying the interplay between nanoscale protein conformations and membrane mechanics is inherently challenging in cell-based experiments. In this work, we investigate the diffusion dynamics of multidrug resistance ABC transporter BmrA as the function of protein conformations: apo (open) or post-hydrolytic (closed) upon in-vitro membrane reconstitution. We perform single-particle tracking measurements on BmrA reconstituted in giant unilamellar vesicles with controlled and varying membrane tensions. We observe a distinct conformation-dependent diffusion profile of BmrA which is inhibited upon increase in membrane tension. Further, experiments involving saturating levels of ATP indicate confinement of proteins to specific “hubs” indicating a new mechanism of protein clustering that competes with membrane tension, and protein enzymatic reactions. Our work gives insights into the intrinsic diffusion dynamics of an active membrane transporter, its interconnection with membrane mechanics, and conformational cycles; all possibly influencing the cell function.