Fig. 2. Engineering ligand-binding domains creates opportunities for translating the biosensing of target molecules into digital signals.

(A) Pyrroloquinoline quinone glucose dehydrogenase (GDH) releases an electron in the presence of glucose, which can be detected using an electrode in a blood-glucose monitor. (B) Split GDH fused to ligand-binding domains (LBDs) for another molecule can be used as a generic biosensor, as the GDH domains can only co-localize to release an electron when the fused LBDs bind to a molecule of interest.