This family includes FlxA from E. coli, Swiss:P77609. The expression of FlxA is regulated by the FliA sigma factor, a transcription factor specific for class 3 flagellar operons. However FlxA is not required for flagellar function or formation [1].

1: Identification of a novel Escherichia coli gene whose expression is dependent on the flagellum-specific sigma factor, FliA, but dispensable for motility development. Ide N, Kutsukake K; Gene. 1997;199:19-23. PMID:9358034