Monobodies: antibody mimics based on the scaffold of the fibronectin type III domain.

We developed the use of the 10th fibronectin type III domain of human fibronectin (FNfn10) as a scaffold to display multiple surface loops for target binding. We termed FNfn10 variants with novel binding function "monobodies." FNfn10 is a small (94 residues) protein with a beta-sandwich structure similar to the immunoglobulin fold. It is highly stable without disulfide bonds or metal ions, and it can be expressed in the correctly folded form at a high level in bacteria. These desirable physical properties render the FNfn10 scaffold compatible with virtually any display technologies. This chapter describes methods for library construction and screening and for the production of monobodies.