Characterization of the myosin-phosphorylating system in normal murine astrocytes and derivative sv40 wild-type and A-mutant transformant

Myosin and myosin light-chain kinase have been isolated and characterized from small quantities of normal and SV40-transformed, murine astrocytic neuroglial cells in culture and from intact normal mouse brain. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis of the astrocyte myosins revealed a heavy chain of 200,000 daltons and two light chains of 20,000 and 15,000 daltons. These myosins are similar to other cytyplasmic myosins. The astrocyte 20,000-dalton light chain can be phosphorylated by an endogenous myosin light-chain kinase which has properties similar to those of the myosin light-chain kinase found in human platelets. No differences were detected in either the astrocyte myosins or myosin light-chain kinases between (a) the normal and transformed cells, (b) the transformed cells grown at the permissive and nonpermissive temperatures, or (c) the SV40 wild-type and A-mutant transformants.