Rat basophilic leukemia mast cells (RBL-2H3) secrete histamine when activated by Ag. This secretion correlates with increased phosphorylation of myosin light chain by protein kinase C (PKC). Calcium ionophores (A23187) also elicit secretion, which is enhanced by PMA.
Full Answer
What happens when myosin light chain is phosphorylated?
We showed that phosphorylation of the myosin regulatory light chain generates a structural signal that is transmitted between myosin molecules in the thick filament and from the thick to the thin filaments, altering their calcium sensitivity.
How does myosin light chain kinase activate myosin?
MLCK is activated by calmodulin in response to an increase in intracellular calcium. It then goes on to phosphorylate regulatory myosin light chains at residues serine 19 and threonine 18 [2][3]. These phosphorylations enhance the ATPase activity of actin-activated myosin and so promotes myosin-driven contraction.
How does the myosin light chain kinase impact myosin activity?
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.
Why is it important to activate Aosin light chain phosphatase MLCP?
Myosin light chain phosphatase (MLCP) is responsible for the dephosphorylation of the regulatory light chain (RLC) of the motor protein myosin-II, and so negatively regulates actomyosin-based contractility.
Does the myosin light chain kinase cause contraction?
Myosin light chain kinase (MLCK), which induces contraction of the perijunctional actomyosin ring through myosin II regulatory light chain phosphorylation, has emerged as a key regulator of the paracellular channel permeability.
How does cAMP inhibit myosin light chain kinase?
Like the heart, the cAMP is broken down by a cAMP-dependent PDE (PDE3). Therefore, inhibition of this enzyme increases intracellular cAMP, which further inhibits myosin light chain kinase thereby producing less contractile force (i.e., promoting relaxation).
What is myosin regulatory light chain?
Myosin regulatory light chain (RLC) is a regulatory subunit of the myosin molecule, which plays a major role in stabilizing the Interacting Head Motif (IHM) of myosin in non-striated muscle.
Does protein kinase A phosphorylate myosin light chain kinase?
Myosin light-chain kinase also known as MYLK or MLCK is a serine/threonine-specific protein kinase that phosphorylates a specific myosin light chain, namely, the regulatory light chain of myosin II.
Which of the following platelet proteins is involved in binding with calcium and in the activation of myosin light chain kinases?
In an actomyosin fraction isolated from human platelets, phosphorylation of the 20,000-dalton light chain of myosin is stimulated by calcium and the calcium-binding protein calmodulin. The enzyme catalyzing this phosphorylation has been isolated by using calmodulin-affinity chromatography.
How does protein kinase C cause contraction?
PKC may also phosphorylate the actin-binding protein calponin, and thereby reverses its inhibition of actin-activated myosin ATPase, allows more actin to interact with myosin, and increases VSM contraction (Figure 1.1) [2].
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 is the role of myosin phosphatase quizlet?
What role does myosin phosphatase play in smooth muscle contraction? It activates when calcium falls below the critical level and removes phosphate from the regulatory chain and contraction stops.