Myosin light-chain kinase
4716916
220281464
2008-06-19T02:48:29Z
75.74.219.214
{{protein
| Name = [[MYLK|myosin, light polypeptide kinase]]
| caption =
| image =
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| 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
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| 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}}