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Title: Inhibition and Structure of Trichomonas vaginalis Purine Nucleoside Phosphorylase with Picomolar Transition State Analogues

Abstract

Trichomonas vaginalis is a parasitic protozoan purine auxotroph possessing a unique purine salvage pathway consisting of a bacterial type purine nucleoside phosphorylase (PNP) and a purine nucleoside kinase. Thus, T. vaginalis PNP (TvPNP) functions in the reverse direction relative to the PNPs in other organisms. Immucillin-A (ImmA) and DADMe-Immucillin-A (DADMe-ImmA) are transition stte mimics of adenosine with geometric and electrostatic features that resemble early and late transition states of adenosine at the transition state stabilized by TvPNP. ImmA demonstrates slow-onset tight-binding inhibition with TvPNP, to give an equilibrium dissociation constant of 87 pM, an inhibitor release half-time of 17.2 min, and a K{sub m}/K{sub d} ratio of 70,100. DADMe-ImmA resembles a late ribooxacarbenium ion transition state for TvPNP to give a dissociation constant of 30 pM, an inhibitor release half-time of 64 min, and a K{sub m}/K{sub d} ratio of 203,300. The tight binding of DADMe-ImmA supports a late S{sub N}1 transition state. Despite their tight binding to TvPNP, ImmA and DADMe-ImmA are weak inhibitors of human and P. falciparum PNPs. The crystal structures of the TvPNP-ImmA{center_dot}PO{sub 4} and TvPNP{center_dot}DADMe-ImmA{center_dot}PO{sub 4} ternary complexes differ from previous structures with substrate anologues. The tight binding with DADMe-ImmA is in part due tomore » a 2.7 {angstrom} ionic interaction between a PO{sub 4} oxygen and the N1 cation of the hydroxypyrrolidine and is weaker in the TvPNP{center_dot}ImmA{center_dot}PO{sub 4} structure at 3.5 {angstrom}. However, the TvPNP{center_dot}ImmA{center_dot}PO{sub 4} structure includes hydrogen bonds between the 2'-hydroxyl and the protein that are not present in TvPNP{center_dot}DADMe-ImmA{center_dot}PO{sub 4}. These structures explain why DADMe-ImmA binds tighter than ImmA. Immucillin-H is a 12 nM inhibitor of TvPNP but a 56 pM inhibitor of human PNP. And this difference is explained by isotope-edited difference infrared spectroscopy with [6-{sup 18}O]ImmH to establish that O6 is the keto tautomer in TvPNP{center_dot}ImmH{center_dot}PO{sub 4}, causing an unfavorable leaving-group interaction.« less

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930356
Report Number(s):
BNL-81075-2008-JA
Journal ID: ISSN 0006-2960; TRN: US200904%%648
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemistry; Journal Volume: 46
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 36 MATERIALS SCIENCE; ADENOSINE; PARASITIC DISEASES; CATIONS; CRYSTAL STRUCTURE; DISSOCIATION; ELECTROSTATICS; HYDROGEN; NUCLEOSIDES; OXYGEN; PHOSPHOTRANSFERASES; PROTEINS; PROTOZOA; PURINES; SPECTROSCOPY; SUBSTRATES; national synchrotron light source

Citation Formats

Rinaldo-Matthis,A., Wing, C., Ghanem, M., Deng, H., Wu, P., Gupta, A., Tyler, P., Evans, G., Furneaux, R., and et al. Inhibition and Structure of Trichomonas vaginalis Purine Nucleoside Phosphorylase with Picomolar Transition State Analogues. United States: N. p., 2007. Web. doi:10.1021/bi061515r.
Rinaldo-Matthis,A., Wing, C., Ghanem, M., Deng, H., Wu, P., Gupta, A., Tyler, P., Evans, G., Furneaux, R., & et al. Inhibition and Structure of Trichomonas vaginalis Purine Nucleoside Phosphorylase with Picomolar Transition State Analogues. United States. doi:10.1021/bi061515r.
Rinaldo-Matthis,A., Wing, C., Ghanem, M., Deng, H., Wu, P., Gupta, A., Tyler, P., Evans, G., Furneaux, R., and et al. Mon . "Inhibition and Structure of Trichomonas vaginalis Purine Nucleoside Phosphorylase with Picomolar Transition State Analogues". United States. doi:10.1021/bi061515r.
@article{osti_930356,
title = {Inhibition and Structure of Trichomonas vaginalis Purine Nucleoside Phosphorylase with Picomolar Transition State Analogues},
author = {Rinaldo-Matthis,A. and Wing, C. and Ghanem, M. and Deng, H. and Wu, P. and Gupta, A. and Tyler, P. and Evans, G. and Furneaux, R. and et al.},
abstractNote = {Trichomonas vaginalis is a parasitic protozoan purine auxotroph possessing a unique purine salvage pathway consisting of a bacterial type purine nucleoside phosphorylase (PNP) and a purine nucleoside kinase. Thus, T. vaginalis PNP (TvPNP) functions in the reverse direction relative to the PNPs in other organisms. Immucillin-A (ImmA) and DADMe-Immucillin-A (DADMe-ImmA) are transition stte mimics of adenosine with geometric and electrostatic features that resemble early and late transition states of adenosine at the transition state stabilized by TvPNP. ImmA demonstrates slow-onset tight-binding inhibition with TvPNP, to give an equilibrium dissociation constant of 87 pM, an inhibitor release half-time of 17.2 min, and a K{sub m}/K{sub d} ratio of 70,100. DADMe-ImmA resembles a late ribooxacarbenium ion transition state for TvPNP to give a dissociation constant of 30 pM, an inhibitor release half-time of 64 min, and a K{sub m}/K{sub d} ratio of 203,300. The tight binding of DADMe-ImmA supports a late S{sub N}1 transition state. Despite their tight binding to TvPNP, ImmA and DADMe-ImmA are weak inhibitors of human and P. falciparum PNPs. The crystal structures of the TvPNP-ImmA{center_dot}PO{sub 4} and TvPNP{center_dot}DADMe-ImmA{center_dot}PO{sub 4} ternary complexes differ from previous structures with substrate anologues. The tight binding with DADMe-ImmA is in part due to a 2.7 {angstrom} ionic interaction between a PO{sub 4} oxygen and the N1 cation of the hydroxypyrrolidine and is weaker in the TvPNP{center_dot}ImmA{center_dot}PO{sub 4} structure at 3.5 {angstrom}. However, the TvPNP{center_dot}ImmA{center_dot}PO{sub 4} structure includes hydrogen bonds between the 2'-hydroxyl and the protein that are not present in TvPNP{center_dot}DADMe-ImmA{center_dot}PO{sub 4}. These structures explain why DADMe-ImmA binds tighter than ImmA. Immucillin-H is a 12 nM inhibitor of TvPNP but a 56 pM inhibitor of human PNP. And this difference is explained by isotope-edited difference infrared spectroscopy with [6-{sup 18}O]ImmH to establish that O6 is the keto tautomer in TvPNP{center_dot}ImmH{center_dot}PO{sub 4}, causing an unfavorable leaving-group interaction.},
doi = {10.1021/bi061515r},
journal = {Biochemistry},
number = ,
volume = 46,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}