1jix
From Proteopedia
T4 Phage BGT in Complex with Ca2+
Structural highlights
FunctionGSTB_BPT4 Catalyzes the transfer of glucose (Glc) from uridine diphosphoglucose (UDP-Glc) to 5-hydroxymethylcytosine (5-HMC) in double-stranded DNA. Is involved in a DNA modification process to protect the phage genome against its own nucleases and the host restriction endonuclease system. Publication Abstract from PubMedbeta-Glucosyltransferase (BGT) is a DNA-modifying enzyme encoded by bacteriophage T4 that transfers glucose from uridine diphosphoglucose to 5-hydroxymethyl cytosine bases of phage T4 DNA. We report six X-ray structures of the substrate-free and the UDP-bound enzyme. Four also contain metal ions which activate the enzyme, including Mg(2+) in forms 1 and 2 and Mn(2+) or Ca(2+). The substrate-free BGT structure differs by a domain movement from one previously determined in another space group. Further domain movements are seen in the complex with UDP and the four UDP-metal complexes. Mg(2+), Mn(2+) and Ca(2+) bind near the beta-phosphate of the nucleotide, but they occupy slightly different positions and have different ligands depending on the metal and the crystal form. Whilst the metal site observed in these complexes with the product UDP is not compatible with a role in activating glucose transfer, it approximates the position of the positive charge in the oxocarbonium ion thought to form on the glucose moiety of the substrate during catalysis. High resolution crystal structures of T4 phage beta-glucosyltransferase: induced fit and effect of substrate and metal binding.,Morera S, Lariviere L, Kurzeck J, Aschke-Sonnenborn U, Freemont PS, Janin J, Ruger W J Mol Biol. 2001 Aug 17;311(3):569-77. PMID:11493010[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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