Am. Zagariya et La. Sitailo, THE INFLUENCE OF ANTIBIOTICS AND ANTITUMOR AGENTS ON THE RELAXATION ACTIVITY OF PISUM-SATIVUM LEAF CHLOROPLAST TOPOISOMERASE-I, Archives of biochemistry and biophysics, 320(1), 1995, pp. 177-181
DNA topoisomerase was isolated from pea leaf chloroplasts. The relaxat
ion activity of this topoisomerase was Mg2+ dependent and sensitive to
ethidium bromide and novobiocin, a gyrase inhibitor. Chloroplast topo
isomerase (Topo I) was ATP independent, as shown by the characteristic
gel distribution of topoisomers. Topoisomerase, compared with the kno
wn eucaryotic topoisomerase I, was not stimulated by polyamines as are
spermidine, spermine, and cadaverine. Ethidium bromide, DAPI, heparin
, nalidixic acid, and m-AMSA (but not camptothecin) were able to inhib
it the relaxation activity of chloroplast topo I. Nalidixic acid, novo
biocin, m-AMSA, camptothecin, and amiloride were tested for their effe
cts on the topo-isomerase-catalyzed ''cleavage complex'' between DNA a
nd chloroplast DNA topoisomerase I. (C) 1995 Academic Press, Inc.