ADP being one of the two major activators (NAD+ being the other one), acts by destabilizing the abortive complexes, and abrogating the negative cooperativity. In the absence of substrates, and with bound ADP, the catalytic cleft is in the open conformation, and the GLUD1 hexamers form long polymers in the crystal cell with more interactions than found in the abortive complex crystals (1NQT). This is consistent with the fact that ADP promotes aggregation in solution. When the catalytic cleft opens, R516 is rotated down on to the phosphates of ADP. The opening of the catalytic cleft is roughly correlated with distance between R516 and phosphates of ADP. In this way, ADP activates GLUD1 by facilitating the opening of the catalytic cleft which decreases product affinity and facilitates product release. thus allowing GLUD1 to reconcile the non-catalytic abortive complexes.