Purification and molecular properties of the toxin coded by Ustilago maydis virus P4

The toxin from the P4 strain of Ustilago maydis was purified and characterized using a series of gel-filtration and ion-exchange columns. The apparent molecular weight of the purified toxin was estimated from gel electrophoresis to be 11.3 kd in the presence of 2-mercaptoethanol and 10.3 kd in the absence of 2-mercaptoethanol. Amino acid analysis indicated 12% basic amino acids, 14% acidic amino acids and 16% glycine. The toxin was also stable to filtration and repeated freezing at -20 degrees C and thawing.