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 and participates in the assembly of the flagellum. Binds to the C-terminal region of flagellin, which is implicated in polymerization, and participates in the assembly of the flagellum (PubMed:16936039). Interacts with translational regulator CsrA (By similarity). Interacts with flagellins FlaB1, FlaB2 and FlaB3. Belongs to the FliW family.