Probing the Conformation and Dynamics of Influenza a M2 Protein using Site-Directed Spin-Label EPR Spectroscopy

Abstract

M2 is a membrane protein critical to the life cycle of influenza A. We have capitalized on the expanding body of high-resolution structural data available for the 97 amino acid M2 protein to design and interpret site-directed spin labeling electron paramagnetic resonance spectroscopy (SDSL-EPR) experiments on the conformation and dynamics of the homotetrameric M2 protein embedded in lipid bilayers. We have obtained data for three different M2 constructs (M2TM 22-46, M2TMC 23-60 and full length M2 protein) spin-labeled at multiple sites within the transmembrane and C-terminal domains. CW and pulsed EPR spectra show evidence that M2 adopts multiple conformational states in bilayers, and that cholesterol content dictates the relative populations of the states.