Vol 42(2008) N 1 p. 79-85;
V.I. Tarasenko1, A.I. Katyshev1, V.F. Kobzev2, Yu.M. Konstantinov1
Comparative analysis of nuclear and mitochondrial DNA topoisomerase I from Zea mays1Siberian Institute of Plant Physiology and Biochemistry, Siberian Division, Russian Academy of Sciences, Irkutsk, 664033, Russia
2Institute of Cytology and Genetics, Siberian Division, Russian Academy of Sciences, Novosibirsk, 630090, Russia
Received - 2007-03-16; Accepted - 2007-04-06
The properties were compared for maize nuclear and mitochondrial DNA topoisomerases I (topo I). Some differences in their ability to bind to single-stranded DNA were revealed. Mitochondrial topo I was active only in the presence of Mg2+, whereas the activity of the nuclear enzyme did not completely depend on Mg2+, although being essentially stimulated in the presence of Mg2+. The mitochondrial enzyme covalently bound to the 5' DNA end, as unique to prokaryotic topo I. The nuclear enzyme, like all eukaryotic topo I, covalently bound to the 3' DNA end. A search for homologous sequences in several databases revealed genes probably encoding mitochondrial topo I in other higher plants. Using cDNA sequencing and in silico analysis, an orthologous gene was revealed in the maize genome. The gene was strongly homologous to the genes encoding prokaryotic topo I, which could explain the differences in properties between mitochondrial and nuclear topo I from maize. The presence of prokaryotic topo I in mitochondria of higher plants is interesting and important for studying the evolution of these plant organelles and the mechanisms of mitochondrial genome expression.
Zea mays, DNA topoisomerase I, mitochondria