STRUCTURE AND PARTIAL AMINO-ACID-SEQUENCE OF CALF THYMUS DNA TOPOISOMERASE-II - COMPARISON WITH OTHER TYPE-II ENZYMES

The partial amino acid sequence of p140 calf thymus DNA topoisomerase II was determined by analysis of cyanogen bromide peptides. Five peptides were aligned and shared extensive homology with sequences derived from cDNA clones for the human topoisomerase II isoenzyme forms. Less homology was seen with the Drosophila, yeast and bacterial type II enzymes. Calf and human enzymes shared epitopes allowing isolation of a cDNA clone to human topoisomerase II isoenzyme α. Our results indicate that calf thymus p140 topoisomerase II is an active N-terminal proteolytic fragment of the native p180 enzyme and demonstrate that mammalian type II enzymes exhibit close sequence similarity. © 1990.