1sxq
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(New page: 200px<br /><applet load="1sxq" size="450" color="white" frame="true" align="right" spinBox="true" caption="1sxq, resolution 1.8Å" /> '''BGT in complex with a...)
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Revision as of 00:42, 21 November 2007
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BGT in complex with a 13mer DNA containing a central C:G base pair and UDP
Overview
Beta-glucosyltransferase (BGT) is a DNA-modifying enzyme and a, glycosyltransferase. This inverting enzyme transfers glucose from, UDP-glucose to the 5-hydroxymethyl cytosine bases of T4 phage DNA. From, previous structural analyses we showed that Asp-100 and Asn-70 were, respectively, the catalytic base and the key residue for specific DNA, recognition (Lariviere, L., Gueguen-Chaignon, V., and Morera, S. (2003) J., Mol. Biol. 330, 1077-1086). Here, we supply biochemical evidence, supporting their essential roles in catalysis. We have also shown, previously that BGT uses a base-flipping mechanism to access, 5-hydroxymethyl cytosine (Lariviere, L., and Morera, S. (2002) J. Mol., Biol. 324, 483-490). Whether it is an active or a passive process remains, unclear, as is the case for all DNA cleaving and modifying enzymes. Here, we report two crystal structures: (i) BGT in complex with a 13-mer DNA, containing an A:G mismatch and (ii) BGT in a ternary complex with UDP and, an oligonucleotide containing a single central G:C base pair. The binary, structure reveals a specific complex with the flipped-out, mismatched, adenine exposed to the active site. Unexpectedly, the other structure, shows the non-productive binding of an intermediate flipped-out base. Our, structural analysis provides clear evidence for a passive process.
About this Structure
1SXQ is a Single protein structure of sequence from Bacteriophage t4 with UDP as ligand. Active as DNA beta-glucosyltransferase, with EC number 2.4.1.27 Full crystallographic information is available from OCA.
Reference
Structural evidence of a passive base-flipping mechanism for beta-glucosyltransferase., Lariviere L, Morera S, J Biol Chem. 2004 Aug 13;279(33):34715-20. Epub 2004 Jun 3. PMID:15178685
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