Myosin light-chain kinase 4716916 220281464 2008-06-19T02:48:29Z 75.74.219.214 {{protein | Name = [[MYLK|myosin, light polypeptide kinase]] | caption = | image = | width = | HGNCid = 7590 | Symbol = [[MYLK]] | AltSymbols = | EntrezGene = 4638 | OMIM = 600922 | RefSeq = NM_053025 | UniProt = Q15746 | PDB = | ECnumber = 2.7.11.18 | Chromosome = 3 | Arm = q | Band = cen | LocusSupplementaryData = -q21 }} {{protein | Name = myosin light chain kinase 2, skeletal muscle | caption = | image = | width = | HGNCid = 16243 | Symbol = MYLK2 | AltSymbols = | EntrezGene = 85366 | OMIM = 606566 | RefSeq = NM_033118 | UniProt = Q9H1R3 | PDB = | ECnumber = | Chromosome = 20 | Arm = q | Band = 13.31 | LocusSupplementaryData = }} '''Myosin-light-chain kinase''' (MLCK) is a [[Serine/threonine-specific protein kinases|serine/threonine-specific protein kinase]] that [[phosphorylate]]s the regulatory light chain of [[myosin II]]. Three different MLCK isoforms exist. There is a cardiac-MLCK encoded by mylk3, a skeletal-MLCK encoded by mylk2, and smooth muscle-MLCK encoded by mylk. Smooth muscle and non-muscle MLCK are identical and are the product of the same gene, mylk. This [[protein]] is important in the mechanism of contraction in [[smooth muscle]]. Once there is an influx of [[calcium]] into the smooth muscle, either from the [[sarcoplasmic reticulum]] or, more important, from the [[extracellular space]], contraction of smooth muscle fibers may begin. First, the calcium will bind to [[calmodulin]]. This binding will activate MLCK, which will go on to phosphorylate the [[myosin|myosin light chain]] at [[serine]] residue 19. This will enable the myosin [[crossbridge]] to bind to the [[actin filament]] and allow contraction to begin (through the [[crossbridge|crossbridge cycle]]). Since smooth muscle does not contain a [[troponin]] complex like [[striated muscle]] does, this mechanism is the main pathway for regulating smooth muscle contraction. ==See also== * [[protein kinase A]] ==External links== * {{MeshName|Myosin-Light-Chain+Kinase}} {{transferase-stub}} {{Serine/threonine-specific protein kinases}}