1kea
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(New page: 200px<br /><applet load="1kea" size="450" color="white" frame="true" align="right" spinBox="true" caption="1kea, resolution 2.00Å" /> '''STRUCTURE OF A THERM...)
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Revision as of 16:59, 20 November 2007
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STRUCTURE OF A THERMOSTABLE THYMINE-DNA GLYCOSYLASE
Overview
The repair of T:G mismatches in DNA is key for maintaining bacterial, restriction/modification systems and gene silencing in higher eukaryotes., T:G mismatch repair can be initiated by a specific mismatch glycosylase, (MIG) that is homologous to the helix-hairpin-helix (HhH) DNA repair, enzymes. Here, we present a 2.0 A resolution crystal structure and, complementary mutagenesis results for this thermophilic HhH MIG enzyme., The results suggest that MIG distorts the target thymine nucleotide by, twisting the thymine base approximately 90 degrees away from its normal, anti position within DNA. We propose that functionally significant, differences exist in DNA repair enzyme extrahelical nucleotide binding and, catalysis that are characteristic of whether the target base is damaged or, is a normal base within a mispair. These results explain why pure HhH DNA, glycosylases and combined glycosylase/AP lyases cannot be interconverted, by simply altering their functional group chemistry, and how, broad-specificity DNA glycosylase enzymes may weaken the glycosylic, linkage to allow a variety of damaged DNA bases to be excised.
About this Structure
1KEA is a Single protein structure of sequence from Methanothermobacter thermautotrophicus with ZN, ACT, CL and SF4 as ligands. Full crystallographic information is available from OCA.
Reference
Structure and activity of a thermostable thymine-DNA glycosylase: evidence for base twisting to remove mismatched normal DNA bases., Mol CD, Arvai AS, Begley TJ, Cunningham RP, Tainer JA, J Mol Biol. 2002 Jan 18;315(3):373-84. PMID:11786018
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