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Nature Structural & Molecular Biology 14, 807–813 (1 September 2007) | doi:10.1038/nsmb1285

Molecular basis of messenger RNA recognition by the specific bacterial repressing clamp RsmA/CsrA

Mario Schubert , Karine Lapouge , Olivier Duss , Florian C Oberstrass , Ilian Jelesarov , Dieter Haas & Fr|[eacute]|d|[eacute]|ric H-T Allain

Proteins of the RsmA/CsrA family are global translational regulators in many bacterial species. We have determined the solution structure of a complex formed between the RsmE protein, a member of this family from Pseudomonas fluorescens, and a target RNA encompassing the ribosome-binding site of the hcnA gene. The RsmE homodimer with its two RNA-binding sites makes optimal contact with an 5|[prime]|-A/UCANGGANGU/A-3|[prime]| sequence in the mRNA. When tightly gripped by RsmE, the ANGGAN core folds into a loop, favoring the formation of a 3-base-pair stem by flanking nucleotides. We validated these findings by in vivo and in vitro mutational analyses. The structure of the complex explains well how, by sequestering the Shine-Dalgarno sequence, the RsmA/CsrA proteins repress translation.