Crystal Structure of Mycobacterium tuberculosis PNP with transition state analog DADMe-ImmH

Experimental Data Snapshot

  • Resolution: 1.90 Å
  • R-Value Free: 0.213 
  • R-Value Work: 0.183 
  • R-Value Observed: 0.186 

Starting Model: experimental
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Over-The-Barrier Transition State Analogues Provide New Chemistries for Inhibitor Design: The Case of Purine Nucleoside Phosphorylase

Lewandowicz, A.Shi, W.Evans, G.B.Tyler, P.C.Furneaux, R.H.Basso, L.A.Santos, D.S.Almo, S.C.Schramm, V.L.

(2003) Biochemistry 42: 6057-6066

  • DOI: https://doi.org/10.1021/bi0343830
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Stable chemical analogues of enzymatic transition states are imperfect mimics since they lack the partial bond character of the transition state. We synthesized structural variants of the Immucillins as transition state analogues for purine nucleoside phosphorylase and characterized them with the enzyme from Mycobacterium tuberculosis (MtPNP). PNPs form transition states with ribooxacarbenium ion character and catalyze nucleophilic displacement reactions by migration of the cationic ribooxacarbenium carbon between the enzymatically immobilized purine and phosphate nucleophiles. As bond-breaking progresses, carbocation character builds on the ribosyl group, the distance between the purine and the carbocation increases, and the distance between carbocation and phosphate anion decreases. Transition state analogues were produced with carbocation character and increased distance between the ribooxacarbenium ion and the purine mimics by incorporating a methylene bridge between these groups. Immucillin-H (ImmH), DADMe-ImmH, and DADMe-ImmG mimic the transition state of MtPNP and are slow-onset, tight-binding inhibitors of MtPNP with equilibrium dissociation constants of 650, 42, and 24 pM. Crystal structures of MtPNP complexes with ImmH and DADMe-ImmH reveal an ion-pair between the inhibitor cation and the nucleophilic phosphoryl anion. The stronger ion-pair (2.7 A) is found with DADMe-ImmH. The position of bound ImmH resembles the substrate side of the transition state barrier, and DADMe-ImmH more closely resembles the product side of the barrier. The ability to probe both substrate and product sides of the transition state barrier provides expanded opportunities to explore transition state analogue design in N-ribosyltransferases. This approach has resulted in the highest affinity transition state analogues known for MtPNP.

  • Organizational Affiliation

    Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Purine Nucleoside Phosphorylase
A, B, C
268Mycobacterium tuberculosisMutation(s): 0 
Find proteins for P9WIL5 (Mycobacterium tuberculosis (strain ATCC 25618 / H37Rv))
Explore P9WIL5 
Go to UniProtKB:  P9WIL5
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP9WIL5
Sequence Annotations
  • Reference Sequence
Small Molecules
Binding Affinity Annotations 
IDSourceBinding Affinity
DIH PDBBind:  1N3I Ki: 1.3 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Resolution: 1.90 Å
  • R-Value Free: 0.213 
  • R-Value Work: 0.183 
  • R-Value Observed: 0.186 
  • Space Group: P 32 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 102.842α = 90
b = 102.842β = 90
c = 128.763γ = 120
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2003-09-30
    Type: Initial release
  • Version 1.1: 2008-04-28
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 2.0: 2018-12-19
    Changes: Atomic model, Data collection, Derived calculations, Non-polymer description, Structure summary
  • Version 2.1: 2023-10-25
    Changes: Data collection, Database references, Derived calculations, Refinement description