A Picomolar MBP-Binding Nanobody for Target Enrichment and Modular Complex Engineering.

The variable domains of heavy chain only antibodies, also called nanobodies, have provided powerful new tools for biomedical research. Their rapid development across multiple fields has helped address emerging scientific and clinical challenges, establishing single-domain antibodies (sdAbs) as highly adaptable platforms for a wide range of biotechnological and therapeutic applications. In this study, we identified a nanobody from an alpaca immune library, sdAbCM1, that binds to the maltose-maltodextrin binding protein, MBP, with picomolar affinity. Biophysical investigations showed that sdAbCM1 recognizes a yet unreported epitope and interacts with MBP in its closed conformation when maltose is present. The high affinity, epitope specificity, and ability to tolerate the ligand-bound state render sdAbCM1 a valuable and versatile biotechnological tool with potential applications such as detection, localization, and purification of MBP fusion proteins and protein complex engineering for single-particle microscopy.