PMID:14711811

Citation	Cheng, B, Feng, J, Gadgil, S and Tse-Dinh, YC (2004) Flexibility at Gly-194 is required for DNA cleavage and relaxation activity of Escherichia coli DNA topoisomerase I. J. Biol. Chem. 279:8648-54
Abstract	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 alpha helix upon G strand DNA binding has been observed from the comparison of the type IA DNA topoisomerase crystal structures. Site-directed mutagenesis of the strictly conserved Gly-194 at the N terminus of this alpha 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.
Links	PubMed Online version:10.1074/jbc.M312095200
Keywords	DNA Topoisomerases, Type I/chemistry; DNA Topoisomerases, Type I/genetics; DNA Topoisomerases, Type I/metabolism; Enzyme Activation; Escherichia coli/enzymology; Glycine; Mutagenesis, Site-Directed; Protein Conformation; Structure-Activity Relationship
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