Alternative binding proteins: Affibody binding proteins developed from a small three‐helix bundle scaffold

Abstract

In recent years, classical antibody‐based affinity reagents have been challenged by novel types of binding proteins developed by combinatorial protein engineering principles. One of these classes of binding proteins of non‐Ig origin are the so‐called affibody binding proteins, functionally selected from libraries of a small (6 kDa), non‐cysteine three‐helix bundle domain used as a scaffold. During the first 10 years since they were first described, high‐affinity affibody binding proteins have been selected towards a large number of targets for use in a variety of applications, such as bioseparation, diagnostics, functional inhibition, viral targeting and in vivo tumor imaging/therapy. The small size offers the possibility to produce functional affibody binding proteins also by chemical synthesis production routes, which has been found to be advantageous for the site‐specific introduction of various labels and radionuclide chelators.