The biochemical basis of the regulation of smooth-muscle contraction.
The primary signal for smooth-muscle contraction is an increase in sarcoplasmic free Ca2+ concentration ([Ca2+]i). This triggers activation of calmodulin-dependent myosin light-chain kinase, which catalyses myosin phosphorylation, thereby activating crossbridge cycling and the development of force or contraction of the muscle cell. Restoration of resting [Ca2+]i deactivates the kinase; myosin is dephosphorylated by myosin light-chain phosphatase and the muscle relaxes. Recent evidence suggests that other signal-transduction pathways can modulate the contractile state of a smooth-muscle cell by affecting specific steps in the myosin phosphorylation-dephosphorylation mechanism.
Allen
B G
BG
Department of Medical Biochemistry, University of Calgary, Alberta, Canada.
Walsh
M P
MP
D000818:Animals; D002118:Calcium / Q000378:metabolism; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D009124:Muscle Proteins / Q000502:physiology; D009130:Muscle, Smooth / Q000378:metabolism* / Q000502:physiology; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D010766:Phosphorylation; D015398:Signal Transduction
D009124:Muscle Proteins; D009219:Myosin-Light-Chain Kinase; D009218:Myosins; D002118:Calcium