Crystal structure of human purine nucleoside phosphorylase complexed with acyclovir

Area of Science:

• Biochemistry
• Structural Biology
• Immunology

Background:

• Human purine nucleoside phosphorylase (HsPNP) degrades deoxyguanosine, and its deficiency causes T-cell immunosuppression.
• HsPNP is a key target for developing inhibitors to modulate T-cell immune responses.
• Structure-based drug design efforts have extensively targeted HsPNP.

Purpose of the Study:

• To report the first crystallographic study of human purine nucleoside phosphorylase (HsPNP) complexed with acyclovir (Acy).
• To analyze structural differences between HsPNP:Acy, PNP apoenzyme, and HsPNP:Immucillin-H.
• To provide a basis for future inhibitor design targeting HsPNP.

Main Methods:

• X-ray crystallography was used to determine the structure of the HsPNP:Acy complex.
• Comparative structural analysis was performed on the HsPNP:Acy complex, apoenzyme, and a known inhibitor complex (HsPNP:Immucillin-H).

Main Results:

• The study presents the first crystal structure of human purine nucleoside phosphorylase complexed with acyclovir (HsPNP:Acy).
• Acyclovir exhibits relatively lower inhibitory activity against HsPNP (K(i)=90 microM) compared to other inhibitors.
• Structural analysis revealed key differences influencing inhibitor binding and refined the understanding of the purine-binding site.

Conclusions:

• The determined HsPNP:Acy structure provides valuable insights into inhibitor binding mechanisms.
• Structural data refines the characterization of the purine-binding site of human purine nucleoside phosphorylase.
• This research serves as a foundation for the rational design of novel HsPNP inhibitors for therapeutic applications.