DIRECT EVIDENCE FOR THE DEOXYRIBONUCLEASE ACTIVITY OF THE PLANT RIBOSOME-INACTIVATING PROTEIN GELONIN

Several plant ribotoxins, including gelonin, were reported to have add itional weak nuclease activities on supercoiled DNA, The potential con tribution of this activity to their cytotoxicity has not been given se rious consideration due to concerns about contaminating nucleases in t he protein preparations. We now report the degradation of single-stran ded DNA by preparations of native plant gelonin and recombinant geloni n produced in E. coli. The DNase activity of both preparations is simi larly modulated by zinc, An SDS-PAGE DNase assay identifies gelonin as the polypeptide responsible for deoxyribonuclease activity. (C) 1997 Federation of European Biochemical Societies.