Structure & Dynamics of Channels and Transporters from Solid-State NMR

Speaker: Dr. Mei Hong, Massachusetts Institute of Technology

Host: Dr. Jinwoo Lee, UMCP

Abstract: Enveloped viruses and bacteria encode membrane-bound ion channels and transporters that are important for the survival and infectivity of these pathogens. Elucidating the structure, dynamics and mechanism of action of these membrane proteins is important for advancing fundamental knowledge of channels and transporters and for developing antiviral and antibiotic drugs. In this lecture I will present our recent determination of the structures and dynamics of the influenza B virus M2 proton channel, the SARS-CoV-2 E cation channel, and the bacterial transporter EmrE. Using multidimensional solid-state NMR spectroscopy and F-based long-range distance measurements, we have determined atomic-resolution structures of these three membrane proteins in phospholipid bilayers. For BM2, the closed and open channel structures explained the proton conduction direction of this channel. Measurement of water H chemical shift anisotropies further showed that water in the channel is anisotropic, suggesting a mechanism with which water mediates proton hopping in the channel pore. The structure of the SARS-CoV-2 E protein shows a triple phenylalanine motif that may be responsible for regulating channel opening. We investigated the structure of substrate-bound EmrE using a novel H-F distance technique. By measuring hundreds of distances between protein amide protons and the fluorinated substrate at neutral and acidic pH, we solved the structures of this canonical bacterial transporter in both its outward-facing and inward-facing states. The two structures provide unprecedented insights into how EmrE uses alternating access to carry out membrane transport.

Biochemistry Seminar