Abstract
The X-ray structure of a putative BenF-like (gene name: PFL1329) protein from Pseudomonas fluorescens Pf-5 (PflBenF) has been determined at 2.6Å resolution. X-ray crystallography revealed a canonical 18-stranded β-barrel fold that forms a central pore with a diameter of ∼4.6Å, which is consistent with the size and physicochemical properties of the presumed aromatic acid substrate, benzoate. Detailed comparisons with the previously-determined structure of Pseudomonas aeruginosa OpdK, a vanillate influx channel, revealed an arginine-rich aromatic acid selectivity filter of nearly identical structure composed of seven highly conserved residues Arg∼Asp∼Arg∼Arg∼Ser∼Asp∼Arg (R∼D∼R∼R∼S∼D∼R sequence motif, where ∼ denotes intervening residues) that define the narrowest part of the pore.