Design of a highly specific glutamine sensor by splitting the glutamine-binding protein

Biosensors Abstract for ligands are versatile tools for biological applications ranging from disease diagnosis to the detection of environmental chemicals. Thus, expanding the repertoire of biosensor toolkits provides novel insights into the unappreciated potentials of molecules. While the natural recognition domains have been employed in current biosensors, their use is limited to the methods such as fluorescence resonance energy transfer sensors or circular permutation. Here, we describe a first-of-its-kind approach that transforms a protein exhibiting ligand-mediated hinge-bending motion into a highly specific fluorescent biosensor. As a proof-of-concept, a glutamine sensor named Q-SHINE (Glutamine sensor via Split HINgE-motion binding protein) was designed by splitting a glutamine-binding protein into two separate stable domains that, in principle, only dimerize in the presence of glutamine. The application of Q-SHINE to determine glutamine concentrations in solution or mouse serum yielded comparable sensitivity and higher specificity to a conventional glutamine assay kit. Moreover, genetically encoded Q-SHINE could effectively monitor intracellular glutamine levels. Aside from highlighting the reliability of a versatile glutamine sensor, our study opens avenues for researchers who wish to explore the application of ligand-binding proteins as biosensors. ### Competing Interest Statement The authors have declared no competing interest.