A translational regulator that binds mRNA to regulate translation initiation and/or mRNA stability. Usually binds in the 5'-UTR at or near the Shine-Dalgarno sequence preventing ribosome-binding, thus repressing translation. Its function is probably anatagonized by FliW. Inhibits translation of flaA mRNA in vitro (PubMed:27353476). Involved in post-transcriptional regulation of flagellin biosynthesis (PubMed:27353476). Homodimer; the beta-strands of each monomer intercalate to form a hydrophobic core, while the alpha-helices form wings that extend away from the core (By similarity). Interacts with FliW (PubMed:27353476). Increased levels of flagellins FlaA and FlaB (PubMed:27353476). In double csrA-fliW deletions flagellin levels are slightly lower than wild-type (PubMed:27353476). Belongs to the CsrA/RsmA family.