Flexibility at Gly-194 Is Required for DNA Cleavage and Relaxation Activity of Escherichia coli DNA Topoisomerase I

• Published in: The Journal of biological chemistry Vol. 279; no. 10; pp. 8648 - 8654
• Main Authors: Cheng, Bokun, Feng, Jingyang, Gadgil, Sharvari, Tse-Dinh, Yuk-Ching
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 05.03.2004; American Society for Biochemistry and Molecular Biology
• Subjects: DNA Topoisomerases, Type I - chemistry; DNA Topoisomerases, Type I - genetics; DNA Topoisomerases, Type I - metabolism; Enzyme Activation; Escherichia coli; Escherichia coli - enzymology; Glycine; Mutagenesis, Site-Directed; Protein Conformation; Structure-Activity Relationship
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M312095200

The proposed mechanism of type IA DNA topoisomerase I includes conformational changes by the single enzyme polypeptide to allow binding of the G strand of the DNA substrate at the active site, and the opening or closing of the “gate” created on the G strand of DNA to the passing single or double DNA strand(s) through the cleaved G strand DNA. The shifting of an α helix upon G strand DNA binding has been observed from the comparison of the type IA DNA topoisomerase crystal structures (Changela, A., DiGate, R. J., and Mondragón, A. (2001) Nature 411, 1077–1081). Site-directed mutagenesis of the strictly conserved Gly-194 at the N terminus of this α helix in Escherichia coli DNA topoisomerase I showed that flexibility around this glycine residue is required for DNA cleavage and relaxation activity and supports a functional role for this hinge region in the enzyme conformational change.