A Prokaryotic Membrane Sculpting BAR Domain Protein

Bin/Amphiphysin/RVS (BAR) domain proteins belong to a superfamily of coiled-coil proteins that influence membrane curvature in eukaryotes and are associated with vesicle biogenesis, vesicle-mediated protein trafficking, and intracellular signaling(-). BAR domain proteins have not been identified in bacteria, despite certain organisms displaying an array of membrane curvature phenotypes(-). Here we identify a prokaryotic BAR domain protein, BdpA, from MR-1, an iron reducing bacterium known to produce redox active membrane vesicles and micrometer-scale membrane extensions. BdpA is required for uniform size distribution of outer membrane vesicles and is responsible for scaffolding outer membrane extensions (OMEs) into membrane structures with consistent diameter and curvature. While a strain lacking BdpA produces OMEs, cryogenic transmission electron microscopy reveals more lobed, disordered OMEs rather than the membrane tubes produced by the wild type strain. Overexpression of BdpA promotes OME formation even during planktonic conditions where OMEs are less common. Heterologous expression also results in OME production in CP1 and . Based on the ability of BdpA to alter membrane curvature , we propose that BdpA and its homologs comprise a newly identified class of prokaryotic BAR (P-BAR) domains that will aid in identification of putative P-BAR proteins in other bacterial species.