This family contains bacterial fibronectin-attachment proteins (FAP). Family members are rich in alanine and proline, are approximately 300 long, and seem to be restricted to mycobacteria. These proteins contain a fibronectin-binding motif that allows mycobacteria to bind to fibronectin in the extracellular matrix [1].

1: Characterization of the fibronectin binding motif for a unique mycobacterial fibronectin attachment protein, FAP. Zhao W, Schorey JS, Groger R, Allen PM, Brown EJ, Ratliff TL; J Biol Chem 1999;274:4521-4526. PMID:9988684