title: Structural polymorphism of c-di-GMP bound to an EAL domain and in complex with a type II PilZ-domain protein.
abstract: Cyclic di-GMP (c-di-GMP) is a novel secondary-messenger molecule that is involved in regulating a plethora of important bacterial activities through binding to an unprecedented array of effectors. Proteins with a canonical PilZ domain that bind c-di-GMP play crucial roles in regulating flagellum-based motility. In contrast, noncanonical type II PilZ domains that do not effectively bind c-di-GMP regulate twitching motility, which is dependent on type IV pili (T4P). Recent data indicate that T4P biogenesis is initiated via the interaction of a noncanonical type II PilZ protein with the GGDEF/EAL-domain protein FimX and the pilus motor protein PilB at high c-di-GMP concentrations. However, the molecular details of such interactions remain to be elucidated. In this manuscript, the first hetero-complex crystal structure between a type II PilZ protein and the EAL domain of the FimX protein (FimX(EAL)) from Xanthomonas campestris pv. campestris (Xcc) in the presence of c-di-GMP is reported. This work reveals two novel conformations of monomeric c-di-GMP in the XccFimX(EAL)-c-di-GMP and XccFimX(EAL)-c-di-GMP-XccPilZ complexes, as well as a unique interaction mode of a type II PilZ domain with FimX(EAL). These findings indicate that c-di-GMP is sufficiently flexible to adjust its conformation to match the corresponding recognition motifs of different cognate effectors. Together, these results represent a first step towards an understanding of how T4P biogenesis is controlled by c-di-GMP at the molecular level and also of the ability of c-di-GMP to bind to a wide variety of effectors.
authors.affiliation: Agricultural Biotechnology Center, National Chung Hsing University, Taichung 40227, Taiwan.
authors.forename: Ko-Hsin
authors.initials: KH
authors.lastname: Chin
authors.forename: Wei-Ting
authors.initials: WT
authors.lastname: Kuo
authors.forename: Yu-Jen
authors.initials: YJ
authors.lastname: Yu
authors.forename: Yi-Ting
authors.initials: YT
authors.lastname: Liao
authors.forename: Ming-Te
authors.initials: MT
authors.lastname: Yang
authors.forename: Shan-Ho
authors.initials: SH
authors.lastname: Chou
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000145:classification / Q000378:metabolism; D018360:Crystallography, X-Ray; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D016959:Xanthomonas campestris / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; C097615:PilZ protein, Pseudomonas aeruginosa; C062025:bis(3',5')-cyclic diguanylic acid; D006152:Cyclic GMP