In smooth muscle, Ca²⁺ binds calmodulin, forming the Ca²⁺-calmodulin complex that activates Myosin Light Chain (MLC) kinase. MLC kinase phosphorylates the regulatory light chains of myosin, enabling cross-bridge cycling and muscle contraction. This differs from skeletal muscle, where Ca²⁺ acts via troponin-tropomyosin on thin filaments. MLC phosphorylation is the key regulatory step in smooth muscle contraction.