Structural highlights
Function[GSTB_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 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. 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[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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