Biopolymers and cell. 1987. Volume 3. № 1. 41 - 43

K. G. Karpenchuk

ATP-INDEPENDENT DNA TOPOISOMERASE FROM THE CHLOROPLASTS OF NICOTIANA CHINENSIS

Summary

    ATP-independent DNA topoisomerase was extracted from the purified leaf chloroplasts of Nicotiana chinensis and partially purified by the salt gradient elution from DEAE-cellulose. Relaxation of negatively supercoiled plasmid pUR222 by the enzyme was found to be absolutely dependent on the presence of magnesium ions, being completely inhibited by EDTA. DNA topoisomerase activity was tolerant to the spermidine (1.8 jxg/ml), novobiocin (80 jxg/ml) and ethidium bromide (0.8 ng/ml). Strong magnesium requirement of chloroplast DNA topoisomerase in ATP-independent reaction resembles properties of the prokaryotic counterparts.