Studies on a Nuclease from Ustilago maydis

Abstract

A nuclease highly active on denatured DNA or RNA has been purified 8,600-fold from the smut fungus Ustilago maydis. The molecular weight of the enzyme is 42,000 as determined by gel filtration. Added divalent cations are not required for activity. Ethylenediaminetetraacetate strongly inhibits activity, but simultaneous addition of an excess of Zn2+ or Co2+ reverses the inhibition. Other inhibitors include potassium phosphate, 2-mercaptoethanol, and ATP. The enzyme has a low level of activity on native DNA. Certain mutant strains which are unable to carry out allelic recombination have reduced amounts of the enzyme. Therefore, this enzyme may play some role in recombination in this organism.