Glia maturation factor in bovine brain: partial purification and physicochemical characterization.

Glia maturation factor (GMF) is partially purified from bovine brains by the following procedure: extraction at physiologic pH, dialysis and freeze-drying of the extract, ethanol washing of the dried powder and re-extraction of the ethanol-washed residue with Tris-buffered saline, ion-exchange chromatography with DEAE Sephadex and molecular sieving with Bio-gel P-200. The partially purified protein has an apparent molecular weight of 23,000 and an isoelectric point of 4.75, and retains both morphological transforming and mitogenic activities when tested on glioblasts. Both activities are susceptible to protease digestion and heat inactivation. The procedure results in a 400-fold purification of the morphological activity and a 1400-fold purification of the mitogenic activity. Both activities are detectable when GMF is used in nanogram quantities. The possibility that both functions are expressions of the same factor and the possible role of GMF in the differential or sequential stimulation of cell growth and maturation are discussed.