Myosin light-chain kinase

Myosin light-chain kinase (MLCK) is a dedicated enzyme that plays a crucial role in muscle contraction and cell motility. It is part of the serine/threonine-specific protein kinase family and is predominantly found in smooth muscle tissues.

Function

MLCK catalyzes the phosphorylation of regulatory light chains of myosin, a process that is essential for muscle contraction. This phosphorylation causes a conformational change in the myosin molecule, enabling it to interact with actin and initiate muscle contraction. In non-muscle cells, MLCK regulates cell shape and motility by controlling the contractility of the actomyosin cytoskeleton.

Structure

MLCK is a large, multidomain protein. The N-terminal domain contains a sequence that binds calmodulin, a calcium-binding messenger protein. The central region of the protein contains a series of immunoglobulin-like domains that may interact with myosin. The C-terminal domain contains the catalytic kinase domain, which phosphorylates the myosin light chains.

Role in Disease

Abnormal MLCK activity has been implicated in several diseases. Overactivity of MLCK can lead to excessive smooth muscle contraction, contributing to conditions such as asthma and hypertension. Conversely, reduced MLCK activity can impair muscle contraction, leading to conditions such as gastroparesis.

See Also

• Myosin
• Muscle contraction
• Serine/threonine-specific protein kinase