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Updated: Jul 29, 2026

Protein-protein Interactions Visualized by Bimolecular Fluorescence Complementation in Tobacco Protoplasts and Leaves
Published on: March 9, 2014
Purification and characterization of a type-I topoisomerase from cultured tobacco cells
S Heath-Pagliuso1, A D Cole, E B Kmiec
1Department of Biochemistry and Biophysics, University of California, Davis, Davis, California 95616.
Abstract:
Cultured tobacco (Nicotiana tabacum, var Xanthi) cells contain a topoisomerase that removes positive and negative supercoils from DNA. The enzyme has an estimated molecular mass of 30,000 daltons under denaturing conditions, but may exist as a multimeric protein in the native state. Activity is enhanced significantly by either MgCl(2) or CaCl(2), but other divalent cations are much less effective in stimulating DNA relaxation. The purified enzyme acts by altering the linking number in topological steps of one and is inhibited by berenil or camptothecin, not novobiocin. Taken together, these data identify this enzyme as a type I topoisomerase.
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