Curli are extracellular functional amyloids that are assembled by enteric bacteria during biofilm formation and host colonization. The csg (curli specific gene) operon encodes major structural and accessory proteins that are required for curli production. The csgBAC operon encodes the major and minor curli fiber components, CsgA and CsgB, respectively. CsgA is secreted to the extracellular milieu as an unfolded protein and forms amyloid polymers upon interacting with the CsgB nucleator [1]. CsgA is comprised of five imperfect repeating units with highly conserved glutamine and asparagine residues that are important for amyloid formation. Each repeating unit is predicted to form a strand-loop-strand motif [2]. In vitro, CsgC inhibits CsgA amyloid formation at substoichiometric concentrations and maintains CsgA in a non-beta-sheet rich conformation, making CsgC an efficient and selective amyloid inhibitor [1].

1: The bacterial curli system possesses a potent and selective inhibitor of amyloid formation. Evans ML, Chorell E, Taylor JD, Aden J, Gotheson A, Li F, Koch M, Sefer L, Matthews SJ, Wittung-Stafshede P, Almqvist F, Chapman MR; Mol Cell. 2015;57:445-455. PMID:25620560

2: Fibrillation of the major curli subunit CsgA under a wide range of conditions implies a robust design of aggregation. Dueholm MS, Nielsen SB, Hein KL, Nissen P, Chapman M, Christiansen G, Nielsen PH, Otzen DE; Biochemistry. 2011;50:8281-8290. PMID:21877724