title: HetR homodimer is a DNA-binding protein required for heterocyst differentiation, and the DNA-binding activity is inhibited by PatS.
abstract: HetR plays a key role in regulation of heterocyst differentiation. When the Cys-48 residue of the HetR from Anabaena sp. PCC 7120 was replaced with an Ala residue, the mutant HetR (HetR(C48A)) could not dimerize, indicating that HetR forms a homodimer through a disulfide bond. The Anabaena strain C48, containing the hetRc48a gene, could not produce HetR homodimer and failed to form heterocyst. We show that HetR is a DNA-binding protein and that its homodimerization is required for the DNA binding. HetR binds the promoter regions of hetR, hepA, and patS, suggesting a direct control of the expression of these genes by HetR. We present evidence that shows that the up-regulation of patS and hetR depends on DNA binding by HetR dimer. The pentapeptide RGSGR, which is present at the C terminus of PatS and blocks heterocyst formation, inhibits the DNA binding of HetR and prevents hetR up-regulation.
authors.affiliation: State Key Laboratory of Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Huang
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Dong
authors.forename: Jindong
authors.initials: J
authors.lastname: Zhao
mesh_terms: D017033:Anabaena / Q000166:cytology*; D001426:Bacterial Proteins / Q000502:physiology*; D001483:Base Sequence; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D019281:Dimerization; D016133:Polymerase Chain Reaction; D020798:Two-Hybrid System Techniques; D015854:Up-Regulation
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; C115380:PatS protein, Anabaena; C067403:HetR protein, Bacteria