Probing the M1-M2 Interaction in Influenza a Virus using Site-Directed Spin Labeling EPR in Lipid Bilayer Nanodiscs

Abstract

Influenza remains a serious global health threat and further characterization of key viral proteins is necessary in order to develop novel drugs and vaccines. Matrix Protein 1 (M1) and Matrix Protein 2 (M2) play key roles in the viral life cycle of Influenza A Virus. M2 is a 97-amino acid membrane bound protein which we have previously studied using site-directed spin labeling EPR and has been shown to have multiple conformational states as well as a critical role in the budding of new viral particles from infected cells. M1 is a 252-amino acid protein with multiple roles, including packaging viral RNA and recruiting it to the budozone through interactions with M2 and other viral membrane proteins. M1 oligomerizes through interactions with other M1 monomers inside the emerging virion. We are using a membrane scaffold protein nanodisc model system with incorporate M2 in order to study how interaction with full-length M1 alters M2 mobility and accessibility to relaxation agents. Nanodiscs allow access to intracellular domains of membrane-bound proteins and are compatible with a number of biophysical assays. Site-directed spin labeling EPR will provide residue-specific information about the conformational changes in M2 due to interactions with M1 and how this interaction contributes to viral budding in Influenza A.