This domain is an adhesive domain that binds to sialoglycan [1]. A Thr-Arg motif conserved across homologous carbohydrate-binding adhesins that may orient the sialic acid moiety of carbohydrate ligands [1].

1: Structural Basis for Sialoglycan Binding by the Streptococcus sanguinis SrpA Adhesin. Bensing BA, Loukachevitch LV, McCulloch KM, Yu H, Vann KR, Wawrzak Z, Anderson S, Chen X, Sullam PM, Iverson TM; J Biol Chem. 2016;291:7230-7240. PMID:26833566