What does activated myosin light chain kinase do?
Abstract. Myosin light chain kinase (MLCK) plays a central role in regulating the actin-myosin interaction of smooth muscle. MLCK phosphorylates the light chain of myosin in the presence of Ca2+ and calmodulin (CaM) thereby activating myosin so that it can interact with actin.
What happens when myosin light chain kinase is phosphorylated?
Myosin light chain kinase from smooth muscle has been shown to be phosphorylated by cyclic AMP-dependent protein kinase, which leads to a decrease in the affinity of the kinase for Ca2+ . calmodulin and, hence, a decrease in enzymatic activity.
How does MLCK cause contraction?
Nipple stimulation during breastfeeding causes a hormone known as oxytocin to be released into your bloodstream. This hormone causes the contraction of all smooth muscles and helps your uterus contract back into its pre-pregnancy shape and size.
What happens when you inhibit myosin light chain kinase?
These data show that, in phasic smooth muscle, inhibition of MLCK causes contraction to fail, despite normal electrical activity and Ca2+ transients.
What role does myosin light chain kinase MLCK perform in smooth muscle that can also be observed in skeletal and cardiac muscle?
The activity of MLCK is central to uterine smooth muscle contraction as its inhibition by wortmanin abolishes contractions, re-affirming that phosphorylation of myosin is essential for force production in the uterus and that MLCK is a major contributor to this force-producing pathway (13).
Where is the myosin light chain kinase?
Myosin light chain kinase (MLCK; EC 2.7. 11.18) is a ubiquitous Ca2+/CaM-activated kinase found in smooth, cardiac and skeletal muscle as well as in mammalian non-muscle cells.
What does a phosphatase do?
A phosphatase is an enzyme that removes a phosphate group from a protein. Together, these two families of enzymes act to modulate the activities of the proteins in a cell, often in response to external stimuli.
What happens when MLC is phosphorylated?
MLC is phosphorylated at multiple sites6,7,8,9. Among them, T18 and S19 are the phosphorylation sites associated with an increase in myosin ATPase activity, the formation of actin filaments such as stress fibers, the stabilization of myosin filaments and cellular contraction, migration and cytokinesis6.
How is MLCK inhibited?
The inhibition can be blocked by the MLCK inhibitor ML-7, indicating that quercetin may be a direct MLCK inhibitor (Zhang et al., 2006).
Is myosin light chain kinase an enzyme?
Myosin light chain kinase (MLCK) is a Ca2+–CaM-dependent enzyme that phosphorylates MLC at Ser-19 or Ser-19/Thr-18 (Dudek and Garcia, 2001; Lazar and Garcia, 1999; Verin et al., 1998a,b; Wadgaonkar et al., 2003). This phosphorylation promotes actin–myosin cross-bridging that leads to cellular contraction.
Is myosin light chain kinase present in cardiac muscle?
A Ca2+/calmodulin-activated myosin light chain kinase is expressed only in cardiac muscle (cMLCK), similar to the tissue-specific expression of skeletal muscle MLCK and in contrast to the ubiquitous expression of smooth muscle MLCK.
Is myosin light chain kinase in skeletal muscle?
Myosin light chain kinase from skeletal muscle regulates an ATP-dependent interaction between actin and myosin by binding to actin. Mol Cell Biochem.
What is myosin light chain kinase?
Myosin light chain kinase (MLCK) is a calcium/calmodulin-dependent serine/threonine kinase, belonging to the immunoglobulin superfamily. It phosphorylates the regulatory myosin light chains of * myosin II, in order to facilitate myosin binding to * actin and therefore aid contractility.
How is myosin light chain phosphatase involved in muscle contraction?
Dephosphorylation of the myosin light chain (and subsequent termination of muscle contraction) occurs through activity of a second enzyme known as myosin light-chain phosphatase (MLCP). Protein kinase C and ROC Kinase are involved in regulating Calcium ion intake; these Calcium ions, in turn stimulate a MYLK, forcing a contraction.
What is the role of MLCK in Myosin-driven contraction?
These phosphorylations enhance the ATPase activity of actin-activated myosin and so promotes myosin-driven contraction. It should however be noted that MLCK itself also has actin binding activity [4], via its N terminal domain [5] [6].