Crystallization and preliminary X-ray diffraction characterization of RpfF, a key DSF synthase from Stenotrophomonas maltophilia.

Stenotrophomonas maltophilia has emerged as a critical nosocomial opportunistic pathogen in the last few years. It is resistant to many clinically useful antibiotics; hence, new ways of combatting this bacterium are essential. Diffusible signal factor (DSF) dependent quorum sensing is a major mechanism of virulence induction in S. maltophilia, with RpfF playing a key role in DSF biosynthesis. Inhibiting S. maltophilia RpfF (SmRpfF) function via small-molecule interference may constitute a new way of treating S. maltophilia infection. SmRpfF was therefore overexpressed in Escherichia coli, purified and crystallized using the hanging-drop vapour-diffusion method. The crystals belonged to the tetragonal space group P4(1)2(1)2 or P4(3)2(1)2, with unit-cell parameters a = b = 148.51, c = 122.82 A, and diffracted to a resolution of 2.25 A.

Crystallization and preliminary X-ray diffraction characterization of an essential protein from Xanthomonas campestris that contains a noncanonical PilZ signature motif yet is critical for pathogenicity.

Recent studies have identified c-di-GMP as a novel secondary messenger molecule that is heavily involved in regulating bacterial biofilm formation, motility, production of pathogenicity factors etc. PilZ domain-containing proteins have been suggested and subsequently proved to be the c-di-GMP receptor. However, considering the diverse biological functions exhibited by c-di-GMP, it may be that receptors other than the PilZ domain exist. An essential protein from the plant pathogen Xanthomonas campestris pv. campestris (Xcc) that contains a noncanonical PilZ signature motif yet is critical for Xcc pathogenicity has been cloned, purified and crystallized. Detailed characterization of this protein may reveal an alternative binding mode of c-di-GMP and allow a more thorough understanding of how c-di-GMP exhibits its diverse effects.