title: Structural basis for inhibition of human PNP by immucillin-H.
abstract: Purine nucleoside phosphorylase (PNP) catalyzes the phosphorolysis of the N-ribosidic bonds of purine nucleosides and deoxynucleosides. PNP is a target for inhibitor development aiming at T-cell immune response modulation. This work reports on the crystallographic study of the complex of human PNP-immucillin-H (HsPNP-ImmH) solved at 2.6A resolution using synchrotron radiation. Immucillin-H (ImmH) inhibits the growth of malignant T-cell lines in the presence of deoxyguanosine without affecting non-T-cell tumor lines. ImmH inhibits activated normal human T cells after antigenic stimulation in vitro. These biological effects of ImmH suggest that this agent may have utility in the treatment of certain human diseases characterized by abnormal T-cell growth or activation. This is the first structural report of human PNP complexed with immucillin-H. The comparison of the complex HsPNP-ImmH with recent crystallographic structures of human PNP explains the high specificity of immucillin-H for human PNP.
mesh_terms: D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D011487:Protein Conformation; D011684:Purine Nucleosides; D011683:Purine-Nucleoside Phosphorylase / Q000037:antagonists & inhibitors* / Q000737:chemistry; D011744:Pyrimidinones / Q000494:pharmacology*; D011758:Pyrroles / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D008024:Ligands; D011684:Purine Nucleosides; D011744:Pyrimidinones; D011758:Pyrroles; C113101:forodesine; D011683:Purine-Nucleoside Phosphorylase