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 main target seems to be the major flagellin gene, while its function is anatagonized by FliW. 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. Belongs to the CsrA/RsmA family.