title: FliW antagonizes CsrA RNA binding by a noncompetitive allosteric mechanism.
abstract: CsrA (carbon storage regulator A) is a widely distributed bacterial RNA binding protein that regulates translation initiation and mRNA stability of target transcripts. In γ-proteobacteria, CsrA activity is competitively antagonized by one or more small RNAs (sRNAs) containing multiple CsrA binding sites, but CsrA in bacteria outside the γ-proteobacteria is antagonized by a protein called FliW. Here we show that FliW of Bacillus subtilis does not bind to the same residues of CsrA required for RNA binding. Instead, CsrA mutants resistant to FliW antagonism (crw) altered residues of CsrA on an allosteric surface of previously unattributed function. Some crw mutants abolished CsrA-FliW binding, but others did not, suggesting that FliW and RNA interaction is not mutually exclusive. We conclude that FliW inhibits CsrA by a noncompetitive mechanism that differs dramatically from the well-established sRNA inhibitors. FliW is highly conserved with CsrA in bacteria, appears to be the ancestral form of CsrA regulation, and represents a widespread noncompetitive mechanism of CsrA control.
authors: Department of Biology, Indiana University, Bloomington, IN 47405;
authors: Sampriti
authors: S
authors: Mukherjee
authors: Department of Biology, Indiana University, Bloomington, IN 47405;
authors: Reid T
authors: RT
authors: Oshiro
authors: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802.
authors: Helen
authors: H
authors: Yakhnin
authors: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802.
authors: Paul
authors: P
authors: Babitzke
authors: Department of Biology, Indiana University, Bloomington, IN 47405; dbkearns@indiana.edu.
authors: Daniel B
authors: DB
authors: Kearns
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites / Q000235:genetics; D001667:Binding, Competitive; D015964:Gene Expression Regulation, Bacterial; D008958:Models, Molecular; D009154:Mutation; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D000072417:Protein Domains; D012313:RNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D016601:RNA-Binding Proteins; D012313:RNA
keywords: CsrA; FliW; Hag; flagella; motility