Abstract
We found that the polymerization of actin was inhibited in the cytoplasm of D- line cells, derived from M1 line, which have lost their ability to differentiate to motile cells during a series of experiments designed to discover how contractile proteins work in the induction of cell motility in a myeloid leukemia cell line (Ml). Serial fractionation by DEAE chromatography, 55-80% saturated ammonium sulfate, Sephadex G150 gel filtration and hydroxylapatite chromatography gave an active fraction that inhibited the polymerization of skeletal muscle actin. This inhibitor (API) was trypsin sensitive, heat labile and had a molecular weight of about 71, 000. The API did not depolymerize F actin.
