Artificial affinity proteins as ligands of immunoglobulins

A number of natural proteins are known to have affinity and specificity for immunoglobulins. Some of them are widely used as reagents for detection or capture applications, such as Protein G and Protein A. However, these natural proteins have a defined spectrum of recognition that may not fit specific needs. With the development of combinatorial protein engineering and selection techniques, it has become possible to design artificial affinity proteins with the desired properties. These proteins, termed alternative scaffold proteins, are most often chosen for their stability, ease of engineering and cost-efficient recombinant production in bacteria. In this review, we focus on alternative scaffold proteins for which immunoglobulin binders have been identified and characterized.