1y6g

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spinqualitylabelsall models 1y6g, resolution 2.8Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

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 Bacteriophage t4 with CL, NCO, UDP and EDO as ligands. Active as DNA alpha-glucosyltransferase, with EC number 2.4.1.26 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

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