Crystal structures of free, IMP-, and GMP-bound Escherichia coli hypoxanthine phosphoribosyltransferase

Guddat, L. W., Vos, S., Martin, J. L., Keough, D. T. and De Jersey, J. (2002) Crystal structures of free, IMP-, and GMP-bound Escherichia coli hypoxanthine phosphoribosyltransferase. Protein Science, 11 7: 1626-1638. doi:10.1110/ps.0201002

Author Guddat, L. W.
Vos, S.
Martin, J. L.
Keough, D. T.
De Jersey, J.
Title Crystal structures of free, IMP-, and GMP-bound Escherichia coli hypoxanthine phosphoribosyltransferase
Journal name Protein Science   Check publisher's open access policy
ISSN 0961-8368
Publication date 2002
Sub-type Article (original research)
DOI 10.1110/ps.0201002
Open Access Status
Volume 11
Issue 7
Start page 1626
End page 1638
Total pages 13
Place of publication Plainview
Publisher Cold Spring Harbor Laboratory Press
Collection year 2002
Language eng
Subject C1
270108 Enzymes
780105 Biological sciences
Abstract Crystal structures have been determined for free Escherichia coli hypoxanthine phosphoribosyltransferase (HPRT) (2.9 Angstrom resolution) and for the enzyme in complex with the reaction products, inosine 5'-monophosphate (IMP) and guanosine 5-monophosphate (GMP) (2.8 Angstrom resolution). Of the known 6-oxopurine phosphoribosyltransferase (PRTase) structures, E. coli HPRT is most similar in structure to that of Tritrichomonas foetus HGXPRT, with a rmsd for 150 Calpha atoms of 1.0 Angstrom. Comparison of the free and product bound structures shows that the side chain of Phe156 and the polypeptide backbone in this vicinity move to bind IMP or GMP. A nonproline cis peptide bond, also found in some other 6-oxopurine PRTases, is observed between Leu46 and Arg47 in both the free and complexed structures. For catalysis to occur, the 6-oxopurine PRTases have a requirement for divalent metal ion, Usually Mg2+ in vivo. In the free structure, a Mg2+, is coordinated to the side chains of Glu103 and Asp104. This interaction may be important for stabilization of the enzyme before catalysis. E. coli HPRT is unique among the known 6-oxopurine PRTases in that it exhibits a marked preference for hypoxanthine as substrate over both xanthine and guanine. The structures suggest that its substrate specificity is due to the modes of binding of the bases. In E. coli HPRT, the carbonyl oxygen of Asp 163 would likely form a hydrogen bond with the 2-exocyclic nitrogen of guanine (in the HPRT-guanine-PRib-PP-Mg2+ complex). However, hypoxanthine does not have a 2-exocyclic atom and the HPRT-IMP structure suggests that hypoxanthine is likely to occupy a different position in the purine-binding pocket.
Keyword Biochemistry & Molecular Biology
Crystal Structure
Purine Salvage
Escherichia Coli
Guanine-xanthine Phosphoribosyltransferase
State Analog Inhibitor
2.0 Angstrom Structure
Ternary Complex
Flexible Loop
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Medicine Publications
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Created: Tue, 14 Aug 2007, 17:30:50 EST