What is the role of calmodulin in smooth muscle contraction?

Calmodulin plays a crucial role in smooth muscle contraction by functioning as a calcium-binding messenger protein. When calcium ions bind to calmodulin, it undergoes a conformational change that allows it to activate myosin light-chain kinase (MLCK). This activation is essential because MLCK phosphorylates myosin light chains, which are necessary for myosin to interact with actin to produce contraction.

The phosphorylation of myosin is a key step in the contractile process of smooth muscle, facilitating the interaction between the actin and myosin filaments. Without the activation of MLCK by calmodulin, smooth muscle contraction would not occur effectively. Therefore, the role of calmodulin in activating MLCK is vital for the regulation and initiation of smooth muscle contraction.