This variable D2 domain is found in uncharacterised proteins from Betaproteobacteria, including Flagellin from Burkholderia pseudomallei (FliC). FliC assembles to form the flagellar filament that supports bacterial motility [1, 2]. The family is found in association with Pfam:PF00669, Pfam:PF00700.

1: Mutagenesis of Burkholderia pseudomallei with Tn5-OT182: isolation of motility mutants and molecular characterization of the flagellin structural gene. DeShazer D, Brett PJ, Carlyon R, Woods DE; J Bacteriol. 1997;179:2116-2125. PMID:9079894

2: Sequence- and Structure-Based Immunoreactive Epitope Discovery for Burkholderia pseudomallei Flagellin. Nithichanon A, Rinchai D, Gori A, Lassaux P, Peri C, Conchillio-Sole O, Ferrer-Navarro M, Gourlay LJ, Nardini M, Vila J, Daura X, Colombo G, Bolognesi M, Lertmemonkolchai G; PLoS Negl Trop Dis. 2015;9:e0003917. PMID:26222657