Probing the Conformation of BamC and BamE in Native Bacterial Membranes Using Solid-State NMR Spectroscopy

Lipoproteins are involved in diverse cellular processes that take place in and around cell membranes. A prominent example refers to the biogenesis of outer membrane proteins mediated by the β-barrel assembly machinery (BAM) that comprises the integral membrane protein BamA and several lipoproteins (BamB-BamE). Using a combination of solid-state NMR spectroscopy in native bacterial settings and molecular dynamics (MD) simulations, we have investigated the structural conformation, dynamics, and topology of lipoproteins BamC and BamE in their native bacterial membrane at the atomic level. We found significant dynamic and topological differences in BamC and BamE when associated with their native membrane settings as compared to their conformation within the fully assembled BAM complex. The combination of these dynamic protein-protein and protein-membrane interactions may be critical to modulating the activity of BamA during BAM-mediated protein insertion.