What is a monobody?

Here at Kerafast, we recently added the first monobody products to our catalog, prompting us to ask the question: what exactly is a monobody?

Monobodies, as it turns out, are actually synthetic binding proteins. Based on a molecular scaffold composed of a fibronection type III domain (FN3), they are an alternative to traditional antibodies, belonging to the class of molecules called antibody mimics. The first paper on monobodies was published in the Journal of Molecular Biology in 1998 by Dr. Shohei Koide and his team at the University of Chicago.

Monobodies are highly specific for their targets and are produced from combinatorial libraries with diversified portions of the FN3 scaffold and mixes of amino acids using phage display or yeast surface display methods. The scaffold is less than 90 residues and is thus very small, enabling expression of a monobody by transfecting your cell of choice with a monobody expression vector. Generally, monobodies act by binding a functional site on target molecules and have been shown to be very effective as highly specific inhibitors.

Since the initial discovery, monobodies have been used for a wide variety of targets and applications resulting in a number of patents. As there are no disulfide bonds in the FN3 scaffold, monobodies may be produced even in reducing environments, a significant advantage they possess over traditional antibodies.   

Clinical trials are ongoing by Adnexus, a biotech company that is now part of Bristol-Myers Squibb, using a class of monobody called adnectins. The compound, pegdinetanib, is an antagonist of vascular endothelial growth factor receptor 2 (VEGFR-2). Planned to be sold under the trade name Angiocept, the drug interferes with angiogenesis near tumors and is undergoing trials for the treatment of glioblastoma, non-small cell lung cancer and colorectal cancer.

Dr. Brian K. Kay’s Mitogen Activated Kinase Kinase 5 (MAP2K5) Monobody used in a pulldown assay. This kinase mediates a signaling cascade involved in growth factor stimulated cell proliferation and muscle cell differentiation.

Kerafast offers seven different monobodies, from the laboratory of Dr. Brian K. Kay at the University of Illinois at Chicago. Several recognize kinases, whereas two are targeted toward ubiquitin. These monobodies have been used in ELISA and pulldown assays.

Another fun fact: Monobody is also the name of an indie-jazz-rock band from Chicago.