This receptor is directly associated with one of its ultimate effectors, the class C L-type calcium channel Ca V . This receptor-channel complex is coupled to the G s G protein , which activates adenylyl cyclase , catalysing the formation of cyclic adenosine monophosphate (cAMP) which then activates protein kinase A , and counterbalancing phosphatase PP2A . Protein kinase A then goes on to phosphorylate (and thus inactivate) myosin light-chain kinase , which causes smooth muscle relaxation, accounting for the vasodilatory effects of beta 2 stimulation. The assembly of the signaling complex provides a mechanism that ensures specific and rapid signaling. A two-state biophysical and molecular model has been proposed to account for the pH and REDOX sensitivity of this and other GPCRs.