Structural subunit of the minor fimbriae. These filamentous pili are attached to the cell surface; they mediate biofilm formation, adhesion onto host cells and onto other bacteria that are part of the oral microbiome. They play an important role in invasion of periodontal tissues and are recognized as major virulence factors. Mfa1 orthologs from different strains have highly divergent sequences, and this correlates with pathogenicity. Structural component of the fimbrial stalk. Minor fimbriae are composed of a structural subunit, most often Mfa1, and the accessory subunits Mfa3, Mfa4 and Mfa5. Mfa1 interacts with Mfa2; this anchors the fimbrium in the membrane. Fimbrium assembly occurs by linear, head-to-tail oligomerization of fimbrial subunits. This is mediated via insertion of a C-terminal beta-strand from one subunit into a groove in the N-terminal domain of the following subunit. Probably synthesized as a palmitoylated precursor. Efficient export to the outer membrane and integration into fimbriae requires lipidation and subsequent proteolytic removal of the lipidated propeptide. Belongs to the bacteroidetes fimbrillin superfamily. FimA/Mfa1 family.