title: Structural basis for the CsrA-dependent modulation of translation initiation by an ancient regulatory protein.
abstract: Regulation of translation is critical for maintaining cellular protein levels, and thus protein homeostasis. The conserved RNA-binding protein CsrA (also called RsmA; for carbon storage regulator and regulator of secondary metabolism, respectively; hereafter called CsrA) represents a well-characterized example of regulation at the level of translation initiation in bacteria. Binding of a CsrA homodimer to the 5'UTR of an mRNA occludes the Shine-Dalgarno sequence, blocking ribosome access for translation. Small noncoding RNAs (sRNAs) can competitively antagonize CsrA activity by a well-understood mechanism. However, the regulation of CsrA by the protein FliW is just emerging. FliW antagonizes the CsrA-dependent repression of translation of the flagellar filament protein, flagellin. Crystal structures of the FliW monomer reveal a novel, minimal β-barrel-like fold. Structural analysis of the CsrA/FliW heterotetramer shows that FliW interacts with a C-terminal extension of CsrA. In contrast to the competitive regulation of CsrA by sRNAs, FliW allosterically antagonizes CsrA in a noncompetitive manner by excluding the 5'UTR from the CsrA-RNA binding site. Our phylogenetic analysis shows that the FliW-mediated regulation of CsrA regulation is the ancestral state in flagellated bacteria. We thus demonstrate fundamental mechanistic differences in the regulation of CsrA by sRNA in comparison with an ancient regulatory protein.
authors.affiliation: LOEWE Center for Synthetic Microbiology, Department of Chemistry, Philipps University Marburg, 35043 Marburg, Germany; gert.bange@synmikro.uni-marburg.de florian.altegoer@synmikro.uni-marburg.de.
authors.forename: Florian
authors.initials: F
authors.lastname: Altegoer
authors.affiliation: Plant Cell Biology, Faculty of Biology, Philipps University Marburg, 35043 Marburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Rensing
authors.affiliation: LOEWE Center for Synthetic Microbiology, Department of Chemistry, Philipps University Marburg, 35043 Marburg, Germany; gert.bange@synmikro.uni-marburg.de florian.altegoer@synmikro.uni-marburg.de.
authors.forename: Gert
authors.initials: G
authors.lastname: Bange
mesh_terms: D000494:Allosteric Regulation; D020816:Amino Acid Motifs; D001412:Bacillus subtilis / Q000145:classification / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005407:Flagella / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D005408:Flagellin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D056506:Geobacillus / Q000145:classification / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D010442:Peptide Chain Initiation, Translational; D010802:Phylogeny; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical; D000072757:Protein Conformation, beta-Strand; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D012329:RNA, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D040681:Structural Homology, Protein
chemical_list: C093587:CsrA protein, E coli; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D012097:Repressor Proteins; D005408:Flagellin
keywords: CsrA; FliW; crystallography; flagellum; translation