Native mass spectrometry (MS) has emerged as a powerful technique for studying the oligomeric state and interactions of membrane proteins. However, native MS can be challenging for smaller and more fragile membrane protein and transmembrane peptide complexes. To address this challenge, we have used native MS to study small viral membrane protein complexes in both detergent micelles and lipid nanodiscs. Using charge reduction reagents for stabilization and advanced data analysis techniques to unravel complex spectra, we discovered that viroporin complexes can be highly sensitive to their environment, showing different oligomeric states in different lipids/detergents, with different pH conditions, and with addition of antiviral drugs. Unexpected oligomeric states have been observed that do not match existing structural models, highlighting previously unseen behavior of these complexes. We have also studied assembly of antimicrobial peptide complexes in lipid nanodiscs. Antimicrobial peptides are also highly sensitive to the lipid environment, showing unique assembly pathways that are controlled by the thickness of the lipid bilayer. Ultimately, we expect these applications of native MS will reveal new insights into the biology of infectious disease and provide new directions for antiviral and antibacterial drug discovery.
Michael Marty (University of Arizona)