2f4q
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(New page: 200px<br /><applet load="2f4q" size="350" color="white" frame="true" align="right" spinBox="true" caption="2f4q, resolution 1.75Å" /> '''Crystal Structure of...)
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Revision as of 17:27, 29 January 2008
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Crystal Structure of Deinococcus radiodurans topoisomerase IB
Overview
Type IB DNA topoisomerases are found in all eukarya, two families of, eukaryotic viruses (poxviruses and mimivirus), and many genera of, bacteria. They alter DNA topology by cleaving and resealing one strand of, duplex DNA via a covalent DNA-(3-phosphotyrosyl)-enzyme intermediate., Bacterial type IB enzymes were discovered recently and are described as, poxvirus-like with respect to their small size, primary structures, and, bipartite domain organization. Here we report the 1.75-A crystal structure, of Deinococcus radiodurans topoisomerase IB (DraTopIB), a prototype of the, bacterial clade. DraTopIB consists of an amino-terminal (N) beta-sheet, domain (amino acids 1-90) and a predominantly alpha-helical, carboxyl-terminal (C) domain (amino acids 91-346) that closely resemble, the corresponding domains of vaccinia virus topoisomerase IB. The five, amino acids of DraTopIB that comprise the catalytic pentad (Arg-137, Lys-174, Arg-239, Asn-280, and Tyr-289) are preassembled into the active, site in the absence of DNA in a manner nearly identical to the pentad, configuration in human topoisomerase I bound to DNA. This contrasts with, the apoenzyme of vaccinia topoisomerase, in which three of the active site, constituents are either displaced or disordered. The N and C domains of, DraTopIB are splayed apart in an "open" conformation, in which the surface, of the catalytic domain containing the active site is exposed for DNA, binding. A comparison with the human topoisomerase I-DNA cocrystal, structure suggests how viral and bacterial topoisomerase IB enzymes might, bind DNA circumferentially via movement of the N domain into the major, groove and clamping of a disordered loop of the C domain around the helix.
About this Structure
2F4Q is a Single protein structure of sequence from Deinococcus radiodurans. Full crystallographic information is available from OCA.
Reference
Crystal structure of a bacterial type IB DNA topoisomerase reveals a preassembled active site in the absence of DNA., Patel A, Shuman S, Mondragon A, J Biol Chem. 2006 Mar 3;281(9):6030-7. Epub 2005 Dec 19. PMID:16368685
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