Figure 1.

Principle of cAMP detection using the engineered GloSensor luciferase. (a) GloSensor luciferase in the open conformation shows negligible activity resulting in a low luminescence background, whereas binding of cAMP to the cAMP binding site favors the closed conformation and hence activates the luciferase, which metabolizes luciferin to oxyluciferin, producing luminescence. (b) Luciferase catalyzes the oxidation of luciferin using molecular oxygen and ATP in the presence of Mg²⁺ to produce oxyluciferin, which is highly unstable in an electronically excited state and produces light upon returning to its electronical ground state. Modified based on published figure [25].