The cyclic-AMP binding domain (CBD) is the central regulatory unit of exchange proteins activated by cAMP (EPAC). The CBD maintains EPAC in a state of auto-inhibition in the absence of the allosteric effector. cAMP. When cAMP binds to the CBD such auto-inhibition is released. https://www.ngetikin.com/amazing-find-Bolia-Loop-Rug-limited-choice/