The role of the carboxyl-terminal amino acid residues in Escherichia coli DNA topoisomerase III-mediated catalysis

Hong Liang Zhang, Swati Malpure, Zhiyu Li, Hiroshi Hiasa, Russell J. DiGate

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

The role that the carboxyl-terminal amino acids of Escherichia coli DNA topoisomerase I (Topo I) and III (Topo III) play in catalysis was examined by comparing the properties of Topo III with those of a truncated enzyme lacking the generalized DNA binding domain of Topo III, Topo I, and a hybrid topoisomerase polypeptide containing the amino-terminal 605 amino acids of Topo III and the putative generalized DNA binding domain of Topo I. The deletion of the carboxyl-terminal 49 amino acids of Topo III decreases the affinity of the enzyme for its substrate, single-stranded DNA, by approximately 2 orders of magnitude and reduces Topo III-catalyzed relaxation of supercoiled DNA and Topo III-catalyzed resolution of DNA replication intermediates to a similar extent. Fusion of the carboxyl-terminal 312 amino acid residues of Topo I onto the truncated molecule stimulates topoisomerase.catalyzed relaxation 15-20-fold, to a level comparable with that of full-length Topo III. However, topoisomerase-catalyzed resolution of DNA replication intermediates was only stimulated 2-3-fold. Therefore, the carboxyl-terminal amino acids of these topoisomerases constitute a distinct and separable domain, and this domain is intimately involved in determining the catalytic properties of these polypeptides.

Original languageEnglish (US)
Pages (from-to)9039-9045
Number of pages7
JournalJournal of Biological Chemistry
Volume271
Issue number15
DOIs
StatePublished - Apr 12 1996

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