Structures of Plasmodium falciparum purine nucleoside phosphorylase complexed with sulfate and its natural substrate inosine

TY - JOUR

T1 - Structures of Plasmodium falciparum purine nucleoside phosphorylase complexed with sulfate and its natural substrate inosine

AU - Schnick, C

AU - Robien, M A

AU - Brzozowski, A M

AU - Dodson, E J

AU - Murshudov, G N

AU - Anderson, L

AU - Luft, J R

AU - Mehlin, C

AU - Hol, W G J

AU - Brannigan, J A

AU - Wilkinson, A J

PY - 2005/9

Y1 - 2005/9

N2 - Purine metabolism in the parasite Plasmodium has been identified as a promising target for antimalarial therapies. Purine nucleoside phosphorylase (PNP) is part of a salvage pathway for the biosynthesis of purines, which are essential for parasite survival. Two crystal structures of PNP from Plasmodium falciparum (PfPNP) in two space groups, each with a single subunit in the asymmetric unit, are described here. One structure, refined to 2.4 angstrom, has an empty nucleoside-binding site and a sulfate ion bound in the phosphate-binding pocket. The second structure, refined to 2.0 angstrom, has the substrate inosine bound to the active centre. Structure comparison reveals alterations in the active site upon ligand binding. The new structures presented here specifically highlight the likely roles of Asp206 and two loops flanking the active site: the beta(7)-alpha(6) loop ( residues similar to 161 - 169) and the beta(9)-alpha(8) loop ( residues similar to 208 - 223). Comparison with PNP in complex with transition-state inhibitors suggests that the purine substrate moves towards the phosphate substrate, rather than vice versa, upon forming the transition state. The single-substrate-containing PfPNP structures also appear to be more flexible than PfPNP bound to inhibitors. Together, these structures serve as a basis for better understanding of ligand binding and mechanism that can be further exploited to optimize the specificity of anti-PfPNP drugs.

AB - Purine metabolism in the parasite Plasmodium has been identified as a promising target for antimalarial therapies. Purine nucleoside phosphorylase (PNP) is part of a salvage pathway for the biosynthesis of purines, which are essential for parasite survival. Two crystal structures of PNP from Plasmodium falciparum (PfPNP) in two space groups, each with a single subunit in the asymmetric unit, are described here. One structure, refined to 2.4 angstrom, has an empty nucleoside-binding site and a sulfate ion bound in the phosphate-binding pocket. The second structure, refined to 2.0 angstrom, has the substrate inosine bound to the active centre. Structure comparison reveals alterations in the active site upon ligand binding. The new structures presented here specifically highlight the likely roles of Asp206 and two loops flanking the active site: the beta(7)-alpha(6) loop ( residues similar to 161 - 169) and the beta(9)-alpha(8) loop ( residues similar to 208 - 223). Comparison with PNP in complex with transition-state inhibitors suggests that the purine substrate moves towards the phosphate substrate, rather than vice versa, upon forming the transition state. The single-substrate-containing PfPNP structures also appear to be more flexible than PfPNP bound to inhibitors. Together, these structures serve as a basis for better understanding of ligand binding and mechanism that can be further exploited to optimize the specificity of anti-PfPNP drugs.

KW - COLI URIDINE PHOSPHORYLASE

KW - TRANSITION-STATE ANALOG

KW - CRYSTAL-STRUCTURE

KW - MACROMOLECULAR STRUCTURES

KW - REFINEMENT

KW - SPECIFICITY

KW - INHIBITORS

KW - ANGSTROM

KW - PROGRAM

U2 - 10.1107/S0907444905020251

DO - 10.1107/S0907444905020251

M3 - Article

SN - 0907-4449

VL - 61

SP - 1245

EP - 1254

JO - Acta Crystallographica. Section D, Biological Crystallography

JF - Acta Crystallographica. Section D, Biological Crystallography

ER -