title: DNA-binding properties of a cGMP-binding CRP homologue that controls development of metabolically dormant cysts of Rhodospirillum centenum.
abstract: Rhodospirillum centenum utilizes 3',5'-cyclic guanosine monophosphate (cGMP) as a messenger to regulate development of desiccation-resistant cysts. In this study, we demonstrated that gcyA, gcyB and gcyC, coding for putative subunits of a guanylyl cyclase, increase expression from 8- to 500-fold when cells transition from vegetative to cyst phases of growth. This induction did not occur in a strain that is defective in cGMP synthesis or in a strain that contains a deletion of cgrA that codes for a cGMP-binding homologue of Escherichia coli catabolite repressor protein (CRP). We also demonstrated that cgrA auto-induces its own expression in the presence of cGMP, indicating that a feed-forward loop is used to ramp up cGMP production as cells undergo encystment. Inspection of an intragenic region upstream of gcyB revealed a sequence that is identical to the CRP consensus sequence from E. coli. DNase I and fluorescence anisotropy analyses demonstrated that CgrA bound to this target sequence at a protein : cGMP ratio of 1 : 2 with Kd ∼61 nM. This was in contrast to CgrA in the presence of cAMP, which exhibited Kd ∼1795 nM. CgrA thus constitutes a novel variant of CRP that utilizes cGMP to regulate production of cGMP synthase for the control of cyst development.
authors.affiliation: Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Sugata
authors.initials: S
authors.lastname: Roychowdhury
authors.affiliation: Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Dong
authors.affiliation: Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Carl E
authors.initials: CE
authors.lastname: Bauer
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D042182:Rhodospirillum centenum / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D017385:Sequence Homology; D013171:Spores, Bacterial / Q000254:growth & development*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D006152:Cyclic GMP