Applications of nanobodies in G protein-coupled receptors research

G protein-coupled receptors (GPCRs), the largest family of transmembrane receptors in the human, contain seven transmembrane helices, and are usually regarded as critical drug targets because of their key roles in multiple diseases. Currently, 30%-40% approved drugs target GPCRs. Nanobodies (also known as single domain antibodies) are important research tools for GPCRs due to their small molecular weight, good biochemical properties and high affinity for "cracks or cavities". In addition, nanobodies have long complementarity determining region 3 (CDR3) loops which can be inserted deeply into GPCRs ligand binding pockets, efficiently binding to the folds. This review summarizes the characteristics of nanobodies and their applications in GPCRs research and briefly introduces the current identification routes of targeted GPCRs nanobodies, which could provide new idea and method for applications of nanobodies in GPCRs research.