The C-terminal amphipathic α-helix of Pseudomonas aeruginosa PelC outer membrane protein is required for its function

Pseudomonas aeruginosa is an opportunistic pathogen, which causes numerous infections and can adopt a versatile lifestyle. During chronic infection, P. aeruginosa becomes established as a bacterial community known as a biofilm. Biofilm formation results from the production of a matrix mainly comprised of exopolysaccharides. P. aeruginosa possesses several gene clusters which contribute to the formation of the matrix, including the pel genes. Among the pel genes, pelC encodes an outer membrane protein, which may serve as a transporter of polysaccharide to the bacterial cell surface. Whereas outer membrane proteins usually display an amphipathic β-barrel fold, we show that PelC requires a C-terminal amphipathic α-helix for outer membrane insertion and function. Such a structural feature has only previously been reported for the Wza outer membrane protein of Escherichia coli, and our data suggest that this characteristic may be found in a large family of proteins, particularly outer membrane proteins specialized in polysaccharide transport.