GTP/ggS-Induced phosphorylation of myosin light chain kinase in smooth muscle

Abstract

Phosphorylation of myosin light chain kinase by a Ca 2+-dependent protein kinase increases the concentration of Ca 2+/calmodulin required for half-maximal activation. The Ca 2+ concentrations required for myosin light chain kinase phosphorylation in permeable smooth muscle are similar to those required for myosin light chain phosphorylation. Both GTPγS and carbachol increase the Ca 2+ sensitivity of myosin light chain kinase phosphorylation as well as light chain phosphorylation. It is proposed that a similar G-protein mediated mechanism regulates the Ca 2+-dependent phosphorylation of these two contractile proteins in smooth muscle.