The function of this region is not clear, but it is found in many flagellar hook proteins, including FliD homologues ([1]). It is normally repeated, but is also apparently seen as a singleton. A conserved IN is seen at the centre of the motif. The diversity of these motifs makes it likely that some members of the family are not identified.

1: Molecular characterization of fliD gene encoding flagellar cap and its expression among Clostridium difficile isolates from different serogroups. Tasteyre A, Karjalainen T, Avesani V, Delmee M, Collignon A, Bourlioux P, Barc MC; J Clin Microbiol 2001;39:1178-1183. PMID:11230454