1K27

Crystal Structure of 5'-Deoxy-5'-Methylthioadenosine Phosphorylase in Complex with a Transition State Analogue


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.95 Å
  • R-Value Free: 0.207 
  • R-Value Work: 0.180 
  • R-Value Observed: 0.183 

wwPDB Validation   3D Report Full Report


This is version 1.2 of the entry. See complete history


Literature

Picomolar transition state analogue inhibitors of human 5'-methylthioadenosine phosphorylase and X-ray structure with MT-immucillin-A

Singh, V.Shi, W.Evans, G.B.Tyler, P.C.Furneaux, R.H.Almo, S.C.Schramm, V.L.

(2004) Biochemistry 43: 9-18

  • DOI: 10.1021/bi0358420
  • Primary Citation of Related Structures:  
    1K27

  • PubMed Abstract: 
  • Methythioadenosine phosphorylase (MTAP) functions solely in the polyamine pathway of mammals to remove the methylthioadenosine (MTA) product from both spermidine synthase (2.5.1.16) and spermine synthase (2.5.1.22). Inhibition of polyamine synthesis is a validated anticancer target ...

    Methythioadenosine phosphorylase (MTAP) functions solely in the polyamine pathway of mammals to remove the methylthioadenosine (MTA) product from both spermidine synthase (2.5.1.16) and spermine synthase (2.5.1.22). Inhibition of polyamine synthesis is a validated anticancer target. We designed and synthesized chemically stable analogues for the proposed transition state of human MTAP on the basis of the known ribooxacarbenium character at all reported N-ribosyltransferase transition states [Schramm, V. L. (2003) Acc. Chem. Res. 36, 588-596]. Methylthio-immucillin-A (MT-ImmA) is an iminoribitol tight-binding transition state analogue inhibitor with an equilibrium dissociation constant of 1.0 nM. The immucillins resemble the ribooxacarbenium ion transition states of N-ribosyltransferases and are tightly bound as the N4' cations. An ion pair formed between the iminoribitol cation and phosphate anion mimics the ribooxacarbenium cation-phosphate anion pair formed at the transition state and is confirmed in the crystal structure. The X-ray crystal structure of human MTAP with bound MT-Imm-A also reveals that the 5'-methylthio group lies in a flexible hydrophobic pocket. Substitution of the 5'-methylthio group with a 5'-phenylthio group gives an equilibrium binding constant of 1.0 nM. Methylthio-DADMe-immucillin-A is a pyrrolidine analogue of the transition state with a methylene bridge between the 9-deazaadenine group and the pyrrolidine ribooxacarbenium mimic. It is a slow-onset inhibitor with a dissociation constant of 86 pM. Improved binding energy with DADMe-immucillin-A suggests that the transition state is more closely matched by increasing the distance between leaving group and ribooxacarbenium mimics, consistent with a more dissociative transition state. Increasing the hydrophobic volume near the 5'-position at the catalytic site with 5'-phenylthio-DADMe-immucillin-A gave a dissociation constant of 172 pM, slightly weaker than the 5'-methylthio group. p-Cl-phenylthio-DADMe-immucillin-A binds with a dissociation constant of 10 pM (K(m)/K(i) value of 500000), the tightest binding inhibitor reported for MTAP. These slow-onset, tight-binding transition state analogue inhibitors are the most powerful reported for MTAP and have sufficient affinity to be useful in inhibiting the polyamine pathway.


    Organizational Affiliation

    Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
5'-Deoxy-5'-Methylthioadenosine PhosphorylaseA283Homo sapiensMutation(s): 0 
Gene Names: MTAPMSAP
EC: 2.4.2.28
UniProt & NIH Common Fund Data Resources
Find proteins for Q13126 (Homo sapiens)
Explore Q13126 
Go to UniProtKB:  Q13126
PHAROS:  Q13126
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ13126
Protein Feature View
Expand
  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
MTM
Query on MTM

Download Ideal Coordinates CCD File 
C [auth A](3S,4R)-2-(4-AMINO-5H-PYRROLO[3,2-D]PYRIMIDIN-7-YL)-5-[(METHYLSULFANYL)METHYL]PYRROLIDINE-3,4-DIOL
C12 H19 N5 O2 S
YLCQGEBEQIBOOJ-BOFBLULFSA-N
 Ligand Interaction
PO4
Query on PO4

Download Ideal Coordinates CCD File 
B [auth A]PHOSPHATE ION
O4 P
NBIIXXVUZAFLBC-UHFFFAOYSA-K
 Ligand Interaction
Binding Affinity Annotations 
IDSourceBinding Affinity
MTM PDBBind:  1K27 Ki: 1 (nM) from 1 assay(s)
Binding MOAD:  1K27 Ki: 1 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.95 Å
  • R-Value Free: 0.207 
  • R-Value Work: 0.180 
  • R-Value Observed: 0.183 
  • Space Group: P 3 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 122.231α = 90
b = 122.231β = 90
c = 44.743γ = 120
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling
CNSrefinement
CNSphasing

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2003-09-30
    Type: Initial release
  • Version 1.1: 2008-04-27
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Derived calculations, Version format compliance