title: How bacterial ribosomal protein L20 assembles with 23 S ribosomal RNA and its own messenger RNA.
abstract: In bacteria, the expression of ribosomal proteins is often feedback-regulated at the translational level by the binding of the protein to its own mRNA. This is the case for L20, which binds to two distinct sites of its mRNA that both resemble its binding site on 23 S rRNA. In the present work, we report an NMR analysis of the interaction between the C-terminal domain of L20 (L20C) and both its rRNA- and mRNA-binding sites. Changes in the NMR chemical shifts of the L20C backbone nuclei were used to show that the same set of residues are modified upon addition of either the rRNA or the mRNA fragments, suggesting a mimicry at the atomic level. In addition, small angle x-ray scattering experiments, performed with the rRNA fragment, demonstrated the formation of a complex made of two RNAs and two L20C molecules. A low resolution model of this complex was then calculated using (i) the rRNA/L20C structure in the 50 S context and (ii) NMR and small angle x-ray scattering results. The formation of this complex is interesting in the context of gene regulation because it suggests that translational repression could be performed by a complex of two proteins, each interacting with the two distinct L20-binding sites within the operator.
authors.affiliation: Cristallographie and RMN Biologiques, UMR 8015 CNRS, Faculté de Pharmacie, 4 Avenue de l'Observatoire, 75006 Paris, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Raibaud
authors.forename: Patrice
authors.initials: P
authors.lastname: Vachette
authors.forename: Maude
authors.initials: M
authors.lastname: Guillier
authors.forename: Frédéric
authors.initials: F
authors.lastname: Allemand
authors.forename: Claude
authors.initials: C
authors.lastname: Chiaruttini
authors.forename: Frédéric
authors.initials: F
authors.lastname: Dardel
mesh_terms: D001426:Bacterial Proteins; D001483:Base Sequence; D001665:Binding Sites; D002850:Chromatography, Gel; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015233:Models, Statistical; D008969:Molecular Sequence Data; D011485:Protein Binding; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012338:RNA, Ribosomal, 23S / Q000737:chemistry* / Q000378:metabolism; D012269:Ribosomal Proteins / Q000737:chemistry* / Q000378:metabolism; D012542:Scattering, Radiation; D013053:Spectrophotometry; D014965:X-Rays
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C040045:L20 ribosomal protein, bacteria; D012333:RNA, Messenger; D012338:RNA, Ribosomal, 23S; D012269:Ribosomal Proteins; C488992:rplT protein, E coli; D012313:RNA