Purification, crystallization and X-ray crystallographic studies of flagellin from Pseudomonas aeruginosa.

Flagellin constitutes the whip-like structure of the bacterial flagellum that is required for locomotion. Upon bacterial invasion into a host, flagellin functions as a pathogen-associated molecular pattern that is recognized by immune receptors, such as Toll-like receptor 5 (TLR5) and NAIP5/NLRC4, and activates host innate immunity against pathogens. Structural and biophysical studies of flagellins have been limited to those of Salmonella species. To better understand the functions of flagellin, it is necessary to study flagellins from other species. In this study, the overexpression, purification and crystallization of Pseudomonas aeruginosa flagellin that lacks the D0 domain (paflagellin-ΔD0) are reported. paflagellin-ΔD0 crystals diffracted to 2.15 Å resolution and belonged to space group C2, with one protein molecule in the asymmetric unit. Future structure-based functional studies of paflagellin would extend the knowledge of the TLR5 or NAIP5/NLRC4 activation mechanisms of flagellin and would make a significant contribution to the design of flagellin vaccines and antiradiation therapeutics.