1ois

<table><tr><td colspan='2'>[[1ois]] is a 1 chain structure with sequence from [http://en.wikipedia.org/wiki/Atcc_18824 Atcc 18824]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1OIS OCA]. For a <b>guided tour on the structure components</b> use [http://proteopedia.org/fgij/fg.htm?mol=1OIS FirstGlance]. <br>

</td></tr><tr id='gene'><td class="sblockLbl"><b>[[Gene|Gene:]]</b></td><td class="sblockDat">TOP1 ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=4932 ATCC 18824])</td></tr>

<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/DNA_topoisomerase DNA topoisomerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.99.1.2 5.99.1.2] </span></td></tr>

<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://proteopedia.org/fgij/fg.htm?mol=1ois FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1ois OCA], [http://pdbe.org/1ois PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=1ois RCSB], [http://www.ebi.ac.uk/pdbsum/1ois PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=1ois ProSAT]</span></td></tr>

[[http://www.uniprot.org/uniprot/TOP1_YEAST TOP1_YEAST]] 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 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-(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 (By similarity).

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== Publication Abstract from PubMed ==

BACKGROUND: Type I DNA topoisomerases, divided mechanistically into two subfamilies, are ubiquitous enzymes that participate in replication and transcription. In addition to its role in these fundamental processes, the biological importance of eukaryotic DNA topoisomerase I is underscored by its identification as the target of the antitumor alkaloid camptothecin. An understanding of the mechanism of catalysis and interactions with camptothecin and other drugs has been hampered by a lack of detailed structural information. RESULTS: The three-dimensional structure of a 26 kDA fragment (residues 135 to about 363) of Saccharomyces cerevisiae DNA topoisomerase I has been determined at 1.9 A resolution. The fragment has a novel architecture comprising a concave platform and a pair of outlying V-shaped helices. Photocrosslinking and protein footprinting experiments show that the positively charged concave surface and the junction region of the V-shaped pair of helices contact DNA in the enzyme-DNA complex. CONCLUSIONS: Crystallographic, biochemical and genetic data indicate that this 26 kDa fragment of yeast DNA topoisomerase I is involved in complex formation between the enzyme and DNA, and probably also in camptothecin-enzyme-DNA ternary complex formation. A molecular model for protein-DNA interaction based on these data is proposed. The bipartite DNA-binding regions of the 26 kDa fragment may enable eukaryotic DNA topoisomerase I to adapt to sequence-dependent structural variations in its DNA substrates.

A 26 kDa yeast DNA topoisomerase I fragment: crystallographic structure and mechanistic implications.,Lue N, Sharma A, Mondragon A, Wang JC Structure. 1995 Dec 15;3(12):1315-22. PMID:8747458<ref>PMID:8747458</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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== References ==

<references/>

[[Category: Atcc 18824]]

[[Category: DNA topoisomerase]]

[[Category: Lue, N]]

[[Category: Mondragon, A]]

[[Category: Sharma, A]]

[[Category: Wang, J C]]

[[Category: Dna-binding protein]]

[[Category: Topoisomerase]]