Partial purification of a morphological transforming factor from pig brain.

A protein that changes one type of embryonic rat brain cell in culture from a primitive morphology to one resembling mature glial cell has been purified 400-fold from pig brain. The procedure includes differential centrifugation, ethanol treatment, trypsin digestion and column chromatography with Sephadex G-200 and Sepharose 4B. Although not completely homogeneous, the protein is biologically active at a concentration of 1-10(-8) M. It has a molecular weight of 350 000 and is heat labile. It is inactivated by the extremes of pH and by 8 M urea. The isoionic point is lower than neutrality. The activity is resistant to DNAase, RNAase, periodate and trypsin, but is susceptible to pronase digestion.