1a41
From Proteopedia
TYPE 1-TOPOISOMERASE CATALYTIC FRAGMENT FROM VACCINIA VIRUS
Structural highlights
Function[TOP1_VACCW] Releases the supercoiling and torsional tension of DNA 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 the specific target site 5'-[CT]CCTTp site in duplex DNA. The scissile phosphodiester is attacked by the catalytic tyrosine of the enzyme, resulting in the formation of a DNA-(3'-phosphotyrosyl)-enzyme intermediate and the expulsion of a 5'-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 5'-OH attacks the covalent intermediate to expel the active-site tyrosine and restore the DNA phosphodiester backbone.[1] [2] 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 PubMedVaccinia DNA topoisomerase breaks and rejoins DNA strands through a DNA-(3'-phosphotyrosyl)-enzyme intermediate. A C-terminal catalytic domain, Topo(81-314), suffices for transesterification chemistry. The domain contains a constellation of five amino acids, conserved in all eukaryotic type IB topoisomerases, that catalyzes attack of the tyrosine nucleophile on the scissile phosphate. The structure of the catalytic domain, consisting of ten alpha helices and a three-strand beta sheet, resembles the catalytic domains of site-specific recombinases that act via a topoisomerase IB-like mechanism. The topoisomerase catalytic pentad is conserved in the tertiary structures of the recombinases despite scant sequence similarity overall. This implies that the catalytic domains of type IB topoisomerases and recombinases derive from a common ancestral strand transferase. Conservation of structure and mechanism between eukaryotic topoisomerase I and site-specific recombinases.,Cheng C, Kussie P, Pavletich N, Shuman S Cell. 1998 Mar 20;92(6):841-50. PMID:9529259[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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