1mw9
From Proteopedia
Crystal Structure of H365R mutant of 67 kDA N-terminal fragment of E. coli DNA Topoisomerase I
Structural highlights
Function[TOP1_ECOLI] Releases the supercoiling and torsional tension of DNA, which is introduced during the DNA replication and transcription, by transiently cleaving and rejoining one strand of the DNA duplex. Introduces a single-strand break via transesterification at a target site in duplex DNA. The scissile phosphodiester is attacked by the catalytic tyrosine of the enzyme, resulting in the formation of a DNA-(5'-phosphotyrosyl)-enzyme intermediate and the expulsion of a 3'-OH DNA strand. The free DNA strand then undergoes passage around the unbroken strand, thus removing DNA supercoils. Finally, in the religation step, the DNA 3'-OH attacks the covalent intermediate to expel the active-site tyrosine and restore the DNA phosphodiester backbone.[1] [2] [3] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedIn order to gain insights into the mechaism of ssDNA binding and recognition by Escherichia coli DNA topoisomerase I, the structure of the 67 kDa N-terminal fragment of topoisomerase I was solved in complex with ssDNA. The structure reveals a new conformational stage in the multistep catalytic cycle of type IA topoisomerases. In the structure, the ssDNA binding groove leading to the active site is occupied, but the active site is not fully formed. Large conformational changes are not seen; instead, a single helix parallel to the ssDNA binding groove shifts to clamp the ssDNA. The structure helps clarify the temporal sequence of conformational events, starting from an initial empty enzyme and proceeding to a ssDNA-occupied and catalytically competent active site. Structure of a complex between E. coli DNA topoisomerase I and single-stranded DNA.,Perry K, Mondragon A Structure. 2003 Nov;11(11):1349-58. PMID:14604525[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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