Measuring Binding at the Putative Melatonin Receptor MT3

Melatonin, (N-acetyl-5-methoxytryptamine), is a neurohormone which possesses a wide range of biological effects. The effects mediated by melatonin are in part attributed to the antioxidant properties of the molecule. For a long time, melatonin had been described as a ligand of a putative "receptor" present in mammalian brains named MT₃. Several studies were thus carried out with the goal of clarifying the nature of this melatonin "receptor." The experimental setup of the binding measurements is unusual. The present chapter aims at describing this technique. This binding site was confirmed independently by several groups, and it was eventually demonstrated that MT3 was the enzyme quinone reductase 2 (NQO2).