Example sentences for: topoisomerase

How can you use “topoisomerase” in a sentence? Here are some example sentences to help you improve your vocabulary:

  • There are two homologous type IA topoisomerases present in E. coli . Topoisomerase III has potent DNA decatenating activity for resolution of plasmid DNA replication intermediates, but much weaker relaxation activity than topoisomerase I [ 17 ] . To exhibit maximal relaxation activity, topoisomerase III requires high temperature (52°C) along with low magnesium and monovalent ion [ 17 18 ] . In contrast, E. coli topoisomerase I was not active in the in vitro assay for resolution of plasmid DNA replication intermediates [ 19 ] . Removal of the C-terminal 49 amino acids from the 653 amino acid topoisomerase III protein resulted in drastic reduction of catalytic activity [ 20 ] . Fusion of the carboxyl-terminal 312 amino acid residues of E. coli topoisomerase I, which includes the entire ZD domain, onto the 605 N-terminal amino acids of topoisomerase III generated a hybrid topoisomerase that has relaxation activity resembling topoisomerase III along with weak decatenating activity [ 21 ] . Although preferring single-stranded DNA as binding substrate, topoisomerase I had been shown to also bind double-stranded DNA [ 22 ] , but there is no data available to indicate which domain in the enzyme is responsible for this interaction.

  • Finally, the in vivo catalytic activities of eukarytotic type IA topoisomerases, the topoisomerase III from various higher organisms may be related to their sequences.

  • This hypothesis could be tested using other DNA topoisomerase poisons known to induce NF-κB [ 34].

  • Removal of negative supercoils from DNA by bacterial type IA topoisomerase involves the following steps: (1) binding of the enzyme to the junction of double-stranded and single-stranded DNA [ 8 ] ; (2) cleavage of a single-strand of DNA near the junction with cleavage sequence preference of a cytosine in the -4 position to form the covalent intermediate [ 9 10 ] ; (3) conformational change of the covalent enzyme-DNA complex to result in physical separation of the 5' phosphate covalently linked to the active tyrosine, and the 3' hydroxyl of the cleaved DNA; (4) passage of the complementary single strand through the break; (5) enzyme conformational change to bring the 5' phosphoryl end back into the proximity of the 3' hydroxyl group of the cleaved DNA; (6) religation of the phosphodiester bond.

  • Escherichia coli DNA topoisomerase I is a representative example of type IA DNA topoisomerase (for reviews, see refs [ 1 2 ] ). Its major biological role in the bacterial cell is the removal of excessive negative supercoils from DNA to maintain the DNA at optimal superhelical density along with DNA gyrase [ 3 ] . The enzyme has a molecular weight of 97 kDa and the active site tyrosine responsible for DNA cleavage is found in the 67 kDa N-terminal transesterification domain.


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