Subcellular distribution of calcium and calmodulin-dependent myosin light chain phosphorylating activity in rat cerebral cortex

The subcellular distribution of Ca²⁺- and calmodulin-dependent myosin light chain phosphorylating activity in rat cerebral cortex was studied. The activity showed a high degree of association to nerve endings (either crude or purified by discontinuous sucrose density gradient centrifugation). After osmotic shock of the nerve endings, the activity was largely membrane associated and could not be released from membranes by freeze-thawing, dilution, 75 mM NaCl or 4 mM EDTA. The association of Ca²⁺/calmodulin-dependent myosin light chain phosphorylating activity with synaptosomal membranes suggests a role of calmodulin-dependent myosin light chain phosphorylation in events relating to neurotransmission.