Purification and further characterization of macrophage 70-kDa protein, a calcium-regulated, actin-binding protein identical to L-plastin

We have previously identified a macrophage 70-kDa, actin-bundling protein as a constituent of actin-based cytoplasmic gel and showed that its association with or dissociation from cytoplasmic gels was remarkably affected by submicromolar calcium. In this study, we purified the 70-kDa protein from soluble cytosolic extracts and carried out a more detailed characterization. The amino acid sequences of four peplidic fragments, obtained from the purified protein by enzymatic or chemical cleavage, were completely or nearly identical to those of L-plastin, a protein initially identified in transformed cells from solid tumors (Goldstein & Leavitt, 1985)