Myosin light-chain kinase

On the other side of the kinase at the N-Terminus end, sits the actin-binding domain, which allows MYLK to form interactions with actin filaments, keeping it in place.

[7] After the influx of calcium ions and the binding to calmodulin, pp60 SRC (a protein kinase) causes a conformational change in MYLK, activating it and resulting in an increase in phosphorylation of myosin light chain at serine residue 19.

Reducing intracellular calcium concentration inactivates MLCK but does not stop smooth muscle contraction since the myosin light chain has been physically modified through phosphorylation(and not via ATPase activity).

[10] In addition to downregulation of MYLK, ROCK indirectly strengthens actin/myosin contraction through inhibiting Cofilin, a protein which depolymerizes actin stress fibers.

[13] Within the cells, MYLK provides an inward pulling force, phosphorylating myosin light chain causing a contraction of the myosin/actin stress fiber complex.

[14] Another source of smooth muscle disorders like ischemia–reperfusion, hypertension, and coronary artery disease arise when mutations to protein kinase C (PKC) result in excessive inhibition of MYLP, which counteracts the activity of MYLK by dephosphorylating myosin light chain.