1k4t
HUMAN DNA TOPOISOMERASE I (70 KDA) IN COMPLEX WITH THE POISON TOPOTECAN AND COVALENT COMPLEX WITH A 22 BASE PAIR DNA DUPLEX
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| , resolution 2.10Å | |||||||
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| Ligands: | , , , , , , , , , | ||||||
| Activity: | DNA topoisomerase, with EC number 5.99.1.2 | ||||||
| Related: | 1A35, 1A31, 1A36, 1K4S
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| Resources: | FirstGlance, OCA, PDBsum, RCSB | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
OverviewOverview
We report the x-ray crystal structure of human topoisomerase I covalently joined to double-stranded DNA and bound to the clinically approved anticancer agent Topotecan. Topotecan mimics a DNA base pair and binds at the site of DNA cleavage by intercalating between the upstream (-1) and downstream (+1) base pairs. Intercalation displaces the downstream DNA, thus preventing religation of the cleaved strand. By specifically binding to the enzyme-substrate complex, Topotecan acts as an uncompetitive inhibitor. The structure can explain several of the known structure-activity relationships of the camptothecin family of anticancer drugs and suggests that there are at least two classes of mutations that can produce a drug-resistant enzyme. The first class includes changes to residues that contribute to direct interactions with the drug, whereas a second class would alter interactions with the DNA and thereby destabilize the drug-binding site.
About this StructureAbout this Structure
1K4T is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.
ReferenceReference
The mechanism of topoisomerase I poisoning by a camptothecin analog., Staker BL, Hjerrild K, Feese MD, Behnke CA, Burgin AB Jr, Stewart L, Proc Natl Acad Sci U S A. 2002 Nov 26;99(24):15387-92. Epub 2002 Nov 8. PMID:12426403
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