This domain is found repeated three times in the N-terminal half of the gliding motility-related SprA proteins. The role of this domain in motility is uncertain [1]. It is also found in proteins required for secretion [2].

1: Flavobacterium johnsoniae SprA is a cell surface protein involved in gliding motility. Nelson SS, Glocka PP, Agarwal S, Grimm DP, McBride MJ; J Bacteriol. 2007;189:7145-7150. PMID:17644580

2: Identification of a Porphyromonas gingivalis novel protein sov required for the secretion of gingipains. Saiki K, Konishi K; Microbiol Immunol. 2007;51:483-491. PMID:17579257