[Purification and biochemical characteristics of actin from the rat malignancy sarcoma-45].

Actin was purified from rat sarcoma-45 by using affinity chromatography on DNase I agarose. Actin was detected in the soluble and cytoskeletal fractions. The molecular mass of the protein was found to be equal to 45 kDa. The tumour actin specifically reacted with the antibody against skeletal muscle actin, inhibited the DNAase I activity and activated in the fibrillar state Mg(2+)-ATPases of sarcoma-45 and skeletal muscle myosins. The activating effect of the tumour protein was lower than that of its skeletal muscle counterpart. V8-protease peptide mapping revealed a similarity between tumour and brain actins. Sarcoma-45 actin was found to contain beta- and gamma-actin isoforms and an unusual isoform which appeared to be more acidic than the alpha-actin isoform.