The major structural element of fimbriae. Required for adherence to saliva-coated hydroxyapatite beads (SHA), an in vitro tooth model. A Fap1-dependent increase in adherence is seen as the pH is reduced from pH 8 to pH 5. Primarily but not exclusively exported by the accessory SecA2/SecY2 protein translocation apparatus. Low expression in early log phase, it increases until stationary phase (at protein level). A monocistronic transcript. Has short and long regions consisting of (E/V/I)S dipeptide repeats. These Ser-rich regions have 28 and 1000 repeats respectively. Glycosylated; occurs within the cytoplasm (PubMed:16997950, PubMed:9632253, PubMed:20164186). It is probable that most of the Ser residues in SSR1 and SSR2 are O-GlcNAcylated. Sequential glycosylation by sugar transferases are able to generate complex sugar polymorphisms (By similarity). Loss of fimbriae on the cell surface, loss of adherence to saliva-coated hydroxyapatite beads (SAH), an in vitro tooth model. Belongs to the serine-rich repeat protein (SRRP) family. It is uncertain whether Met-1 or Met-18 is the initiator. Truncated N-terminus.