A novel tetrameric PilZ domain structure from xanthomonads.

PilZ domain is one of the key receptors for the newly discovered secondary messenger molecule cyclic di-GMP (c-di-GMP). To date, several monomeric PilZ domain proteins have been identified. Some exhibit strong c-di-GMP binding activity, while others have barely detectable c-di-GMP binding activity and require an accessory protein such as FimX to indirectly respond to the c-di-GMP signal.

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.

XC1028 from Xanthomonas campestris adopts a PilZ domain-like structure without a c-di-GMP switch.

The crystal structure of XC1028 from Xanthomonas campestris has been determined to a resolution of 2.15 A using the multiple anomalous dispersion approach. It bears significant sequence identity and similarity values of 64.