PAK pilA, pilA, Pilin, PAK pilin, fimbrial protein, type 4 fimbrial protein PilA, type IV fimbrial protein
Pathogenic bacteria, such as Pseudomonas aeruginosa, have developed a variety of virulence factors facilitating the infection process. A prominent virulence factor are pilins essentially required for attachment of the pathogen to the host cell and thus to initiate an infection. Pilins of P. aeruginosa are polymers of non-covalently associated pilA monomers that form a fiber with a diameter of six nm and a length of up to several micrometers. These fibers are polar and dynamic, retractable structures that are regarded as prototypes of type IV pili. Although each pilA monomer has a receptor binding site, only the monomers at the pilus tip have functional binding sites mediating adhesion. Binding occurs at glycosylated receptors that contain a β-D-GalNAc (1 → 4)-β-D-Gal moiety, such as the glycolipids asialo-GM1 and asialo-GM2. Strikingly, pilin fibers of different bacterial strains are sometimes highly divergent, but all strains still seem to bind a common receptor, asialo-GM1. Structural elucidation of pilin variants is essential for the development of effective vaccines that block adhesion of pathogens to host cells. Successful crystallization of the pilin monomer pilA from the P. aeruginosa strain PAK was enabled by truncation of the hydrophobic N-terminus to increase solubility without hindering receptor binding capacities. Here, an N-terminally His-tagged variant of the truncated PAK pilin is available.
