Function
Acts as an anti-CsrA protein, binds CsrA and prevents it from repressing translation of its target genes, one of which is flagellin. Binds to flagellin (hag), which is implicated in polymerization, and participates in the assembly of the flagellum (PubMed:16936039). An antagonist to translational regulator CsrA, it binds CsrA at an allosteric site and non-competitively inhibits CsrA binding to hag RNA (PubMed:27516547). Partner switching by flagellin between FliW and CsrA provides a flagellar assembly checkpoint to tightly control the timing of flagellin synthesis. Flagellin binds to assembly factor FliW, freeing translation regulator CsrA to repress translation of the flagellin mRNA. When the flagellar hook is assembled flagellin is secreted, depleting intracellular flagellin, which frees FliW to interact with CsrA and inhibits CsrA binding to mRNA. This derepresses flagellin translation and provides protein for flagellar assembly. Once the flagellar filament is completed cytoplasmic flagellin levels rise and CsrA translation repression of flagellin reinitiates (PubMed:21895793). Binds to CsrA and displaces it from hag mRNA (PubMed:21895793, PubMed:27516547). Binds to hag mRNA itself, but only at much higher concentrations than those required to displace CsrA (PubMed:21895793, PubMed:27516547).