|PROSITE documentation PDOC00333|
DNA topoisomerase I (EC 18.104.22.168) [1,2,3,4] is one of the two types of enzyme that catalyze the interconversion of topological DNA isomers. Type I topoisomerases act by catalyzing the transient breakage of DNA, one strand at a time, and the subsequent rejoining of the strands. When a prokaryotic type I topoisomerase breaks a DNA backbone bond, it simultaneously forms a protein-DNA link where the hydroxyl group of a tyrosine residue is joined to a 5'-phosphate on DNA, at one end of the enzyme-severed DNA strand.
Prokaryotic organisms, such as Escherichia coli, have two type I topoisomerase isozymes: topoisomerase I (gene topA) and topoisomerase III (gene topB). Eukaroytes also contain homologs of prokaryotic topoisomerase III.
There are a number of conserved residues in the region around the active site tyrosine; we used this region as a signature pattern.Last update:
December 2004 / Pattern and text revised.
PROSITE method (with tools and information) covered by this documentation:
|Source||Curr. Opin. Cell Biol. 1:533-535(1989).|
|2||Authors||Sharma A., Mondragon A.|
|Source||Curr. Opin. Struct. Biol. 5:39-47(1995).|
|Source||Curr. Opin. Struct. Biol. 1:99-103(1991).|
|Title||The mechanisms of DNA topoisomerases.|
|Source||Trends Biochem. Sci. 20:156-160(1995).|