Partial purification and characterization of a cell specific G1-inhibitor (chalone) from JB-1 ascites tumors

Cell-specific G₁-inhibitory (chalone) activity has been extracted from old JB-1 ascites tumors and purified by means of G-15 Sephadex chromatography. Four peaks of activity were obtained, the amount of activity in each peak varying from batch to batch. The first eluting activity peak probably represents chalone activity present in an aggregated form. The latest eluting activity peak was totally unspecific and could be attributed to the presence of high amounts of salts. The two intermediary peaks of activity were investigated in more detail. It is shown that the first eluting activity peak of these two is due to the polyamine spermine complexed to a carrier. Although the spermine complex exhibits a certain degree of cell-specific inhibitory activity in vitro, it is totally inactive in vivo. The second eluting activity peak containing the main part of cell-specific G-inhibitory activity has been characterized as a small molecular weight (M_r300–600), ampholytic, hydrophobic, slightly acidic, and thiol-containing peptide active both in vitro and in vivo.