PROSITE documentation PDOC00333Prokaryotic DNA topoisomerase I active site
DNA topoisomerase I (EC 5.99.1.2) [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.
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PROSITE method (with tools and information) covered by this documentation:
| 1 | Authors | Sternglanz R. |
| Title | DNA topoisomerases. | |
| Source | Curr. Opin. Cell Biol. 1:533-535(1989). | |
| PubMed ID | 2560656 |
| 2 | Authors | Sharma A. Mondragon A. |
| Title | DNA topoisomerases. | |
| Source | Curr. Opin. Struct. Biol. 5:39-47(1995). | |
| PubMed ID | 7773745 |
| 3 | Title | Bjornsti M.-A. |
| Source | Curr. Opin. Struct. Biol. 1:99-103(1991). |
| 4 | Authors | Roca J. |
| Title | The mechanisms of DNA topoisomerases. | |
| Source | Trends Biochem. Sci. 20:156-160(1995). | |
| PubMed ID | 7770916 |
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