Stretching to 1.7 times the resting length of porcine carotid arteries reversibly prevents active tension development by K+ or norepinephrine stimulation. The 20,000-dalton light chain of myosin was maximally phosphorylated in the stretched noncontracting muscles, equal to that in the nonstretched contracting muscles challenged with K+ or norepinephrine. These results show that the contractile ...

Myosin light-chain phosphorylation is the primary mechanism for activating smooth-muscle contraction and occurs principally at Ser-19 of the 20 kDa light chains of myosin (LC(20)). In some circumstances, Thr-18 phosphorylation may also occur. Protein kinase C (PKC) can regulate LC(20) phosphorylation indirectly via signalling pathways leading to inhibition of myosin light-chain phosphatase. The...

The spatial distribution of molecular signals within cells is crucial for cellular functions. Here, as a model to study the polarized spatial distribution of molecular activities, we used cells on micropatterned strips of fibronectin with one end free and the other end contacting a neighbouring cell. Phosphoinositide 3-kinase and the small GTPase Rac display greater activity at the free end, wh...

Calmodulin is the major intracellular Ca(2+)-binding protein, providing Ca(2+)-dependent regulation of numerous intracellular enzymes. The phosphorylation of calmodulin may provide an additional mechanism for modulating its function as a signal transducer. Phosphocalmodulin has been identified in tissues and cells, and calmodulin is phosphorylated both in vitro and in intact cells by various en...