Immunological identification of human platelet mitochondrial DNA topoisomerase I.
A nuclear human blood platelets have been used to study mitochondrial topoisomerase activity in the absence of nuclear contamination. Previous work utilizing this novel system demonstrated that platelet mitochondria contain type-I topoisomerase (Kosovsky, M.J. and Soslau, G. (1991) Biochim. Biophys. Acta 1078, 56-62). The present work has demonstrated that mitochondrial topoisomerase activity was inhibited by the specific topoisomerase-I inhibitor, topotecan, yet was not affected by a specific topoisomerase-II inhibitor, VM-26. These results confirm that platelet mitochondria contain topoisomerase I, yet do not contain a detectable level of topoisomerase-II activity. It has been demonstrated for the first time that antibodies directed against nuclear topo I cross-react with mitochondria topo I. Furthermore, immunoblot analysis of platelet mitochondrial proteins, in conjunction with renaturation studies, has led to the identification of a catalytically active 60-kDa form of mitochondrial topoisomerase I.
Department of Biological Chemistry, Hahnemann University, Philadelphia, PA 19102.
M J
MJ
Kosovsky
G
G
Soslau
D000974:Antibodies, Antinuclear / Q000494:pharmacology; D001792:Blood Platelets / Q000201:enzymology*; D002460:Cell Line / Q000201:enzymology; D004264:DNA Topoisomerases, Type I / Q000032:analysis* / Q000737:chemistry; D006801:Humans; D008928:Mitochondria / Q000201:enzymology; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000032:analysis; D059004:Topoisomerase I Inhibitors
D000974:Antibodies, Antinuclear; D009687:Nuclear Proteins; D059004:Topoisomerase I Inhibitors; D004264:DNA Topoisomerases, Type I