MLCK (Myosin Light Chain Kinase) primarily includes smooth muscle and non-muscle types, each possessing a kinase domain and regulatory regions. MLCK is expressed in tissues such as the heart, smooth muscles, and brain, mainly involved in regulating cell contraction and movement. The kinase modulates muscle contraction and other cellular motility processes by phosphorylating myosin light chains on actin filaments. Gene expression varies across tissues, and related mutations can lead to muscular dysfunctions.