Figure 1. Regulation of vascular smooth muscle contraction by myosin phosphorylation.

Activation of α-adrenoceptors (α-AR) increases intracellular Ca²⁺, which binds to calmodulin and activates myosin light chain (MLC) kinase, resulting in phosphorylation of the 20 kDa regulatory light chains of myosin and smooth muscle contraction. G, heterotrimeric G protein.