title: Dynamic complex formation between HD-GYP, GGDEF and PilZ domain proteins regulates motility in Xanthomonas campestris.
abstract: RpfG is a member of a class of wide spread bacterial two-component regulators with an HD-GYP cyclic di-GMP phosphodiesterase domain. In the plant pathogen Xanthomonas campestris, RpfG together with the sensor kinase RpfC regulates multiple factors as a response to the cell-to-cell Diffusible Signalling Factor (DSF). A dynamic physical interaction of RpfG with two diguanylate cyclase (GGDEF) domain proteins controls motility. Here we show that, contrary to expectation, regulation of motility by the GGDEF domain proteins does not depend upon their cyclic di-GMP synthetic activity. Furthermore we show that the complex of RpfG and GGDEF domain proteins recruits a specific PilZ domain 'adaptor' protein, and this complex then interacts with the pilus motor proteins PilU and PiIT. The results support a model in which DSF signalling influences motility through the highly regulated dynamic interaction of proteins that affect pilus action. A specific motif that we identify to be required for HD-GYP domain interaction is conserved in a number of GGDEF domain proteins, suggesting that regulation via interdomain interactions is of broad relevance.
authors.affiliation: BIOMERIT Research Centre, Department of Microbiology, BioSciences Institute, University College Cork, Cork, Ireland. r.ryan@ucc.ie
authors.forename: Robert P
authors.initials: RP
authors.lastname: Ryan
authors.forename: Yvonne
authors.initials: Y
authors.lastname: McCarthy
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Kiely
authors.forename: Rosemary
authors.initials: R
authors.lastname: O'Connor
authors.forename: Chuck S
authors.initials: CS
authors.lastname: Farah
authors.forename: Judith P
authors.initials: JP
authors.lastname: Armitage
authors.forename: J Maxwell
authors.initials: JM
authors.lastname: Dow
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016959:Xanthomonas campestris / Q000737:chemistry / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C419552:RpfG protein, Xanthomonas campestris; D036781:Fimbriae Proteins