Engineering fibronectin-based binding proteins by yeast surface display.

Yeast surface display (YSD) presents proteins on the surface of yeast through interaction of the agglutinin subunits Aga1p and Aga2p. The human 10th type III fibronectin (Fn3) is a small, 10-kDa protein domain that maintains its native fold without disulfide bonds. A YSD library of Fn3s has been engineered with a loop amino acid composition similar to that of human antibody complementarity-determining region heavy chain loop 3 (CDR-H3) and varying loop lengths, which has been shown to improve binding ability. There are many advantages of using these small, stable domains that maintain binding capabilities similar to that of antibodies. Here, we outline a YSD methodology to isolate Fn3 binders to a diverse set of target antigens.