Crystal structure of orotate phosphoribosyltransferase. | Academic Article individual record
abstract

Phosphoribosyltransferases (PRTases) are enzymes involved in the synthesis of purine, pyrimidine, and pyridine nucleotides. They utilize alpha-D-5-phosphoribosyl-1-pyrophosphate (PRPP) and a nitrogenous base to form a beta-N-riboside monophosphate and pyrophosphate (PPi), and their functional significance in nucleotide homeostasis is evidenced by the devastating effects of inherited diseases associated with the decreased activity and/or stability of these enzymes. The 2.6-A structure of the Salmonella typhimurium orotate phosphoribosyltransferase (OPRTase) complexed with its product orotidine monophosphate (OMP) provides the first detailed image of a member of this group of enzymes. The OPRTase three-dimensional structure was solved using multiple isomorphous replacement methods and reveals two major features: a core five-stranded alpha/beta twisted sheet and an N-terminal region that partially covers the C-terminal portion of the core. PRTases show a very high degree of base specificity. In OPRTase, this is determined by steric constraints and the position of hydrogen bond donors/acceptors of a solvent-inaccessible crevice where the orotate ring of bound OMP resides. Crystalline OPRTase is a dimer, with catalytically important residues from each subunit available to the neighboring subunit, suggesting that oligomerization is necessary for its activity. On the basis of the presence of a common PRPP binding motif among PRTases and the similar chemistry these enzymes perform, we propose that the alpha/beta core found in OPRTase will represent a common feature for PRTases. This generality is demonstrated by construction of a model of the human hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) from secondary structure predictions for HGPRTase and the three-dimensional structure of OPRTase.

author list (cited authors)
Scapin, G., Grubmeyer, C., & Sacchettini, J. C.
publication date
1994
published in
BIOCHEMISTRY Journal
keywords
  • Crystallography, X-Ray
  • Nucleotides
  • Macromolecular Substances
  • Crystallization
  • Electrochemistry
  • Molecular Structure
  • Molecular Sequence Data
  • Amino Acid Sequence
  • Protein Structure, Secondary
  • Hypoxanthine Phosphoribosyltransferase
  • Binding Sites
  • Orotate Phosphoribosyltransferase
  • Hydrogen Bonding
  • Models, Molecular
altmetric score

3.0

citation count

90