Crystallization and preliminary X-ray diffraction characterization of the XccFimX ^EAL-c-di-GMP and XccFimX ^EAL-c-di-GMP-XccPilZ complexes from Xanthomonas campestris

c-di-GMP is a major secondary-messenger molecule in regulation of bacterial pathogenesis. Therefore, the c-di-GMP-mediated signal transduction network is of considerable interest. The PilZ domain was the first c-di-GMP receptor to be predicted and identified. However, every PilZ domain binds c-di-GMP with a different binding affinity. Intriguingly, a noncanonical PilZ domain has recently been found to serve as a mediator to link FimX ^EAL to the PilB or PilT ATPase to control the function of type IV pili (T4P). It is thus essential to determine the structure of the FimX ^EAL-PilZ complex in order to determine how the binding of c-di-GMP to the FimX ^EAL domain induces conformational change of the adjoining noncanonical PilZ domain, which may transmit information to PilB or PilT to control T4P function. Here, the preparation and preliminary X-ray diffraction studies of the XccFimX ^EAL-c-di-GMP and XccFimX ^EAL-c-di-GMP-XccPilZ complexes from Xcc (Xanthomonas campestris pv. campesteris) are reported. Detailed studies of these complexes may allow a more thorough understanding of how c - di-GMP transmits its effects through the degenerate EAL domain and the noncanonical PilZ domain.