Naslov
Calf spleen purine nucleoside phosphorylase : structure of its ternary complex with an N(7)- acycloguanosine inhibitor and a phosphate anion

Autori
Luić, Marija ; Koellner, Gertraud ; Shugar, David ; Saenger, Wolfram ; Bzowska, Agnieszka

Izvornik
Acta crystallographica. Section D, Biological crystallography (0907-4449) 57 (2001); 30-36

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
PNP

Sažetak
The calf spleen purine nucleoside phosphorylase (PNP) ternary complex with an N(7)-acycloguanosine inhibitor and a phosphate ion has been crystallized in the cubic space group P2(1)3, with unit-cell parameter a = 94.11 Angstrom and one monomer per asymmetric unit. X-ray diffraction data were collected using synchrotron radiation (Station X31, EMBL Outstation, DESY, Hamburg). The crystal structure was refined to a resolution of 2.2 Angstrom and R and R-free values of 17.5 and 24.5%, respectively. The acyclonucleoside inhibitor is bound in the active site in an inverted ('upside- down') orientation of the purine base compared with natural substrates. The side chain of Asp243 forms two hydrogen bonds with the base ring: N-delta donates a hydrogen to N(3) and O-delta accepts a hydrogen from the guanine N(2)-amino group. N(1)-H of the base is hydrogen bonded to O-delta of Glu201, while N(9) accepts a hydrogen bond from Thr242 O-gamma. In addition, a water molecule (W417) bridges the N(2)-amino group of the base and O-epsilon of Glu201. In the phosphate-binding site, a phosphate ion is bound to Ser33, His64, Arg84, His86, Ala116 and Ser220. The acyclic chain of the N(7)-acycloguanosine inhibitor is in a folded conformation and together with a water molecule (W388) occupies the pentose- binding site, with possible hydrogen bonds to Tyr88 O-eta and His257 N-delta1. This new binding mode fully accounts for the previously observed substrate properties of 7-beta -D- ribofuranosides of hypoxanthine and guanine. It also provides a new starting point for the design of inhibitors of PNP for therapeutic and other applications.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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