Structure of the outer membrane porin OmpW from the pervasive pathogen Klebsiella pneumoniae

Conjugation is the process by which plasmids, including those that carry antibiotic-resistance genes, are mobilized from one bacterium (the donor) to another (the recipient). The conjugation efficiency of IncF-like plasmids relies on the formation of mating-pair stabilization via intimate interactions between outer membrane proteins on the donor (a plasmid-encoded TraN isoform) and recipient bacteria. Conjugation of the R100-1 plasmid into Escherichia coli and Klebsiella pneumoniae (KP) recipients relies on pairing between the plasmid-encoded TraN alpha in the donor and OmpW in the recipient. Here, the crystal structure of K. pneumoniae OmpW (OmpW(KP)) is reported at 3.2 angstrom resolution. OmpW(KP) forms an eight-stranded.-barrel flanked by extracellular loops. The structures of E. coli OmpW (OmpW(EC)) and OmpW(KP) show high conservation despite sequence variability in the extracellular loops.