Members of this family are pilin major subunits whose structure includes an LPXTG motif-containing signal (see TIGR01167) near the C-terminus, for processing by sortases. Most contain a recognizable D2-type fimbrial isopeptide formation domain (see TIGR04226), in which Lys-to-Asn isopeptide bond formation provides additional structural integrity to support adhesion despite shear. For proper members of this subfamily, lengths fall typically in the range of 460 to 640 amino acids in length. Many members of this family contribute to the virulence of certain Gram-positive pathogens, including SpaA, SpaD, and SpaH from Corynebacterium diphtheriae, and EbpB and EbpC from Enterococcus faecalis.
Jiyao W et al.(2023). "The conserved domain database in 2023.",