A 1.4 A crystal structure for the hypoxanthine phosphoribosyltransferase of Trypanosoma cruzi.
The hypoxanthine phosphoribosyltransferase (HPRT) from Trypanosoma cruzi, etiologic agent of Chagas' disease, was cocrystallized with the inosine analogue Formycin B (FmB) and the structure determined to 1.4 A resolution. This is the highest resolution structure yet reported for a phosphoribosyltransferase (PRT), and the asymmetric unit of the crystal contains a dimer of closely associated, nearly identical subunits. A conserved nonproline cis peptide in one active-site loop exposes the main-chain nitrogen to the enzyme active site, while the adjacent lysine side chain interacts with the other subunit of the dimer, thereby providing a possible mechanism for communication between the subunits and their active sites. The three-dimensional coordinates for the invariant Ser103-Tyr104 dipeptide are reported here for the first time. These are the only highly conserved residues in a second active-site loop, termed the long flexible loop, which is predicted to close over the active site of HPRTs to protect a labile transition state [Eads et al. (1994) Cell 78, 325-334]. This structure represents a major step forward in efforts to design/discover potent selective inhibitors of the HPRT of T. cruzi.
Focia
P J
PJ
Laboratory of Molecular Parasitology & Drug Design, School of Pharmacy, University of North Carolina, Chapel Hill 27599-7360, USA.
Craig
S P
SP
Nieves-Alicea
R
R
Fletterick
R J
RJ
Eakin
A E
AE
D000818:Animals; D001665:Binding Sites; D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D014349:Trypanosoma cruzi / Q000201:enzymology*
D011994:Recombinant Proteins; D007041:Hypoxanthine Phosphoribosyltransferase