PURIFICATION AND CHARACTERIZATION OF 2 DNA-BINDING PROTEINS FROM THE BASIDIOMYCETE LENTINUS-EDODES

Two DNA-binding proteins were purified from the basidiomycete Lentinus edodes (designated LE1 and LE2). The molecular weights of LE1 and LE2 were estimated to be 58,000 and 42,600, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. LE1 had a maximum DNA-binding activity at pH 3.5-4.0 and was inactive at pHs higher than 6. In contrast, LE2 was active at pHs ranging from 3.5 to 10.0; the activity at pH 7.5 was about a half of the optimum activity at 3.5-4.5. Zn2+, Ca2+, and Mn2+ stimulated the activities of LE1 and LE2. Both LE1 and LE2 had a preference for negatively superhelical and nicked circular DNA rather than the linear form. Sufficient amounts of LE1 and LE2 converted the DNA to a form hardly entering an agarose gel. LE1 and LE2 also showed an affinity for single-stranded DNA but not for tRNA. Of interest was the fact that LE2 enhances L. edodes topoisomerase I acitivity under appropriate conditions.