A protein scaffold based on a consensus sequence of fibronectin type III (FN3) proteins, such as the tenth FN3 repeat from human fibronectin (human Tenascin), including isolated nucleic acids that encode a protein scaffold, vectors, host cells, and methods of making and using thereof have applications in diagnostic and/or therapeutic compositions, methods and devices. In particular, protein scaffold molecules binding to IgG have been identified as useful for diagnostic and/or therapeutic applications.