Phosphorylation of lymphocyte myosin catalyzed in vitro and in intact cells.

Abstract

Myosin was isolated from guinea pig B-lymphocytic leukemia cells (L2C). The myosin was enzymatically phosphorylated and dephosphorylated in vitro with both heterologous and lymphocyte-derived enzymes. Both the H chain and 20,000-dalton L chain of lymphocyte myosin were phosphorylated in vitro. Phosphorylation of myosin enhanced actin-activated ATPase activity. Phosphorylation of myosin in murine lymphocytes was analyzed by a novel technique for rapid immunoprecipitation of myosin from cell extracts. Both the chain and 20,000-dalton L chain of myosin were phosphorylated in intact cells. Addition of antibody reactive with cell-surface Ig to lymphocyte populations enriched from B cells stimulated locomotion of these cells and also increased the quantity of 32P isolated in association with the 20,000-dalton L chain of lymphocyte myosin, when 32Pi was present in the medium. An unidentified, phosphorylated polypeptide with a molecular mass of 22,000 daltons was coisolated with myosin from cells by rapid immunoprecipitation. Phosphorylation of myosin may contribute to regulation of movements performed by lymphocytes which are related to their participation in immunologic reactions.