Advances in solid-state NMR studies of microbial rhodopsins

Abstract

Microbial rhodopsins are membrane-embedded heptahelical proteins which are responsible for ion transport or signal transduction in cells. Whereas initial research focused on the four microbial rhodopsins found in Halobacterium Salinarium and related haloarchaea, many additional members have been recently discovered in eubacteria and eukarya, and their structures and functions have been extensively studied. Solid-state nuclear magnetic resonance (NMR) spectroscopy is unique among structural and biophysical methods in that it reports on a structure of a membrane protein in its native-like lipid-embedded state. Here we review the developments in solid-state NMR and highlight its recent contributions to the structural studies of microbial rhodopsins.