1y6g
From Proteopedia
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'''alpha-glucosyltransferase in complex with UDP and a 13_mer DNA containing a HMU base at 2.8 A resolution''' | '''alpha-glucosyltransferase in complex with UDP and a 13_mer DNA containing a HMU base at 2.8 A resolution''' | ||
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[[Category: Morera, S.]] | [[Category: Morera, S.]] | ||
[[Category: Sommer, N.]] | [[Category: Sommer, N.]] | ||
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| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 15:55:46 2008'' | |
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Revision as of 12:55, 3 May 2008
alpha-glucosyltransferase in complex with UDP and a 13_mer DNA containing a HMU base at 2.8 A resolution
Overview
The Escherichia coli T4 bacteriophage uses two glycosyltransferases to glucosylate and thus protect its DNA: the retaining alpha-glucosyltransferase (AGT) and the inverting beta-glucosyltransferase (BGT). They glucosylate 5-hydroxymethyl cytosine (5-HMC) bases of duplex DNA using UDP-glucose as the sugar donor to form an alpha-glucosidic linkage and a beta-glucosidic linkage, respectively. Five structures of AGT have been determined: a binary complex with the UDP product and four ternary complexes with UDP or UDP-glucose and oligonucleotides containing an A:G, HMU:G (hydroxymethyl uracyl) or AP:G (apurinic/apyrimidinic) mismatch at the target base-pair. AGT adopts the GT-B fold, one of the two folds known for GTs. However, while the sugar donor binding mode is classical for a GT-B enzyme, the sugar acceptor binding mode is unexpected and breaks the established consensus: AGT is the first GT-B enzyme that predominantly binds both the sugar donor and acceptor to the C-terminal domain. Its active site pocket is highly similar to four retaining GT-B glycosyltransferases (trehalose-6-phosphate synthase, glycogen synthase, glycogen and maltodextrin phosphorylases) strongly suggesting a common evolutionary origin and catalytic mechanism for these enzymes. Structure-guided mutagenesis and kinetic analysis do not permit identification of a nucleophile residue responsible for a glycosyl-enzyme intermediate for the classical double displacement mechanism. Interestingly, the DNA structures reveal partially flipped-out bases. They provide evidence for a passive role of AGT in the base-flipping mechanism and for its specific recognition of the acceptor base.
About this Structure
1Y6G is a Single protein structure of sequence from Enterobacteria phage t4. Full crystallographic information is available from OCA.
Reference
Structural evidence of a passive base-flipping mechanism for AGT, an unusual GT-B glycosyltransferase., Lariviere L, Sommer N, Morera S, J Mol Biol. 2005 Sep 9;352(1):139-50. PMID:16081100 Page seeded by OCA on Sat May 3 15:55:46 2008
