1B8N

PURINE NUCLEOSIDE PHOSPHORYLASE


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2 Å
  • R-Value Free: 0.246 
  • R-Value Work: 0.164 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Atomic dissection of the hydrogen bond network for transition-state analogue binding to purine nucleoside phosphorylase

Kicska, G.A.Tyler, P.C.Evans, G.B.Furneaux, R.H.Shi, W.Fedorov, A.A.Lewandowicz, A.Cahill, S.M.Almo, S.C.Schramm, V.L.

(2002) Biochemistry 41: 14489-14498


  • PubMed Abstract: 
  • Immucillin-H (ImmH) and immucillin-G (ImmG) were previously reported as transition-state analogues for bovine purine nucleoside phosphorylase (PNP) and are the most powerful inhibitors reported for the enzyme (K(i) = 23 and 30 pM). Sixteen new immuci ...

    Immucillin-H (ImmH) and immucillin-G (ImmG) were previously reported as transition-state analogues for bovine purine nucleoside phosphorylase (PNP) and are the most powerful inhibitors reported for the enzyme (K(i) = 23 and 30 pM). Sixteen new immucillins are used to probe the atomic interactions that cause tight binding for bovine PNP. Eight analogues of ImmH are identified with equilibrium dissociation constants of 1 nM or below. A novel crystal structure of bovine PNP-ImmG-PO(4) is described. Crystal structures of ImmH and ImmG bound to bovine PNP indicate that nearly every H-bond donor/acceptor site on the inhibitor is fully engaged in favorable H-bond partners. Chemical modification of the immucillins is used to quantitate the energetics for each contact at the catalytic site. Conversion of the 6-carbonyl oxygen to a 6-amino group (ImmH to ImmA) increases the dissociation constant from 23 pM to 2.6 million pM. Conversion of the 4'-imino group to a 4'-oxygen (ImmH to 9-deazainosine) increases the dissociation constant from 23 pM to 2.0 million pM. Substituents that induce small pK(a) changes at N-7 demonstrate modest loss of affinity. Thus, 8-F or 8-CH(3)-substitutions decrease affinity less than 10-fold. But a change in the deazapurine ring to convert N-7 from a H-bond donor to a H-bond acceptor (ImmH to 4-aza-3-deaza-ImmH) decreases affinity by >10(7). Introduction of a methylene bridge between 9-deazahypoxanthine and the iminoribitol (9-(1'-CH(2))-ImmH) increased the distance between leaving and oxacarbenium groups and increased K(i) to 91 000 pM. Catalytic site energetics for 20 substitutions in the transition-state analogue are analyzed in this approach. Disruption of the H-bond pattern that defines the transition-state ensemble leads to a large decrease in binding affinity. Changes in a single H-bond contact site cause up to 10.1 kcal/mol loss of binding energy, requiring a cooperative H-bond pattern in binding the transition-state analogues. Groups involved in leaving group activation and ribooxacarbenium ion stabilization are central to the H-bond network that provides transition-state stabilization and tight binding of the immucillins.


    Related Citations: 
    • Calf Spleen Purine Nucleoside Phosphorylase Complexed with Substrates and Substrate Analogs
      Mao, C.,Cook, W.J.,Zhow, M.,Fedorov, A.A.,Almo, S.C.,Ealick, S.E.
      (1998) Biochemistry 37: 7135


    Organizational Affiliation

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




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
PURINE NUCLEOSIDE PHOSPHORYLASE
A
284Bos taurusGene Names: PNP (NP)
EC: 2.4.2.1
Find proteins for P55859 (Bos taurus)
Go to Gene View: PNP
Go to UniProtKB:  P55859
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
PO4
Query on PO4

Download SDF File 
Download CCD File 
A
PHOSPHATE ION
O4 P
NBIIXXVUZAFLBC-UHFFFAOYSA-K
 Ligand Interaction
MG
Query on MG

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Download CCD File 
A
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
IMG
Query on IMG

Download SDF File 
Download CCD File 
A
1,4-DIDEOXY-1,4-IMINO-1-(S)-(9-DEAZAGUANIN-9-YL)-D-RIBITOL
IMMUCILLIN-G
C11 H15 N5 O4
KBIDJCVAURJXFG-PVEDRDFWSA-N
 Ligand Interaction
External Ligand Annotations 
IDBinding Affinity (Sequence Identity %)
IMGKi: 0 - 42 nM (88) BINDINGDB
9DGKd: 160 - 170 nM (99) BINDINGDB
IMGKi: 0.03 nM BINDINGMOAD
IMGKi: 0.03 nM PDBBIND
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2 Å
  • R-Value Free: 0.246 
  • R-Value Work: 0.164 
  • Space Group: P 21 3
Unit Cell:
Length (Å)Angle (°)
a = 90.320α = 90.00
b = 90.320β = 90.00
c = 90.320γ = 90.00
Software Package:
Software NamePurpose
X-PLORmodel building
DENZOdata reduction
SCALEPACKdata scaling
X-PLORphasing
X-PLORrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 1999-02-08
    Type: Initial release
  • Version 1.1: 2008-04-26
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Derived calculations, Version format compliance