Membrane Protein Structures and Ligand Binding From Solid-State NMR

Membrane proteins carry out a myriad of cellular functions such as ion conduction, metabolite transport, and signaling. Solid-state NMR spectroscopy allows us to obtain detailed atomic information of membrane protein structures and dynamics that underlie these functions. I will present our investigations of the structure and dynamics of two viral membrane proteins. The influenza virus M2 protein transports protons across the viral lipid envelope and conducts membrane scission. We have not only characterized the structural dynamics that underlies proton transport, but also determined how cholesterol binds M2 to mediate membrane scission. The cholesterol-bound protein structure gave unexpected insight into how M2 is attracted to the neck of the budding virus to cause membrane curvature. In a second study, we have determined the structure and assembly of the C-terminal membrane-associated region of the HIV fusion protein, gp41. Both these studies extensively employ ¹⁹F NMR of fluorinated protein or ligand. Fluorine is a high-sensitivity nuclear spin with many favorable NMR properties. We have developed a collection of¹⁹F-based NMR techniques for high-field and fast magic-angle-spinning conditions, to measure inter-atomic distances to a much higher upper limit (~ 2 nm) than possible by¹³CNMR.