Assessing the Protonation State and Dynamics of His37 in the Influenza M2 Proton Channel using Raman Spectroscopy

The influenza M2 protein is known to shuttle protons into the virion, facilitating replication and maturation. Histidine 37 is thought to provide “shuttling” activity to those protons, but the protonation states of the four His37 residues in the tetrameric channel has not been definitively established. We use Raman spectroscopy to collect the frequency of a C2-D probe group on His-37 in an isotopically labeled version of the M2 transmembrane peptide. The C2-D frequency reports directly on the protonation state of selected His residues in a way that other experiments cannot. The data are used to identify His37 protonation states in various pH conditions and to report directly on the activity and dynamics of His37 with protons and water in its local environment.