Thiophosphorylation of the 130-kDa subunit is associated with a decreased activity of myosin light chain phosphatase in alpha-toxin-permeabilized smooth muscle.
Pretreatment of alpha-toxin-permeabilized smooth muscle with ATP gamma S (adenosine 5'-O-(thiotriphosphate)) under conditions resulting in minimal (< 1%) thiophosphorylation of the myosin light chain increases the subsequent calcium sensitivity of force output and myosin light chain phosphorylation. The change in calcium sensitivity results at least in part from a 5-fold decrease in myosin light chain phosphatase activity. One of the few proteins thiophosphorylated under these conditions is the 130-kDa subunit of myosin light chain phosphatase. These results suggest that thiophosphorylation of this subunit leads to a decrease in the activity of the phosphatase, and that phosphorylation and dephosphorylation of the subunit may play a role in regulating myosin light chain phosphatase activity.
Trinkle-Mulcahy
L
L
Department of Physiology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Ichikawa
K
K
Hartshorne
D J
DJ
Siegman
M J
MJ
Butler
T M
TM
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002463:Cell Membrane Permeability; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D043263:Myosin-Light-Chain Phosphatase; D009218:Myosins / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010750:Phosphoproteins / Q000302:isolation & purification; D010766:Phosphorylation; D011817:Rabbits; D010738:Type C Phospholipases / Q000187:drug effects
D010750:Phosphoproteins; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate; D010749:Phosphoprotein Phosphatases; D043263:Myosin-Light-Chain Phosphatase; D010738:Type C Phospholipases; D009218:Myosins