10MH

TERNARY STRUCTURE OF HHAI METHYLTRANSFERASE WITH ADOHCY AND HEMIMETHYLATED DNA CONTAINING 5,6-DIHYDRO-5-AZACYTOSINE AT THE TARGET


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.55 Å
  • R-Value Work: 0.205 
  • R-Value Observed: 0.205 

wwPDB Validation   3D Report Full Report


This is version 1.2 of the entry. See complete history


Literature

Mechanism of inhibition of DNA (cytosine C5)-methyltransferases by oligodeoxyribonucleotides containing 5,6-dihydro-5-azacytosine.

Sheikhnejad, G.Brank, A.Christman, J.K.Goddard, A.Alvarez, E.Ford Jr., H.Marquez, V.E.Marasco, C.J.Sufrin, J.R.O'gara, M.Cheng, X.

(1999) J Mol Biol 285: 2021-2034

  • DOI: 10.1006/jmbi.1998.2426
  • Primary Citation of Related Structures:  
    10MH

  • PubMed Abstract: 
  • A key step in the predicted mechanism of enzymatic transfer of methyl groups from S-adenosyl-l-methionine (AdoMet) to cytosine residues in DNA is the transient formation of a dihydrocytosine intermediate covalently linked to cysteine in the active site of a DNA (cytosine C5)-methyltransferase (DNA C5-MTase) ...

    A key step in the predicted mechanism of enzymatic transfer of methyl groups from S-adenosyl-l-methionine (AdoMet) to cytosine residues in DNA is the transient formation of a dihydrocytosine intermediate covalently linked to cysteine in the active site of a DNA (cytosine C5)-methyltransferase (DNA C5-MTase). Crystallographic analysis of complexes formed by HhaI methyltransferase (M.HhaI), AdoMet and a target oligodeoxyribonucleotide containing 5-fluorocytosine confirmed the existence of this dihydrocytosine intermediate. Based on the premise that 5,6-dihydro-5-azacytosine (DZCyt), a cytosine analog with an sp3-hybridized carbon (CH2) at position 6 and an NH group at position 5, could mimic the non-aromatic character of the cytosine ring in this transition state, we synthesized a series of synthetic substrates for DNA C5-MTase containing DZCyt. Substitution of DZCyt for target cytosines in C-G dinucleotides of single-stranded or double-stranded oligodeoxyribonucleotide substrates led to complete inhibition of methylation by murine DNA C5-MTase. Substitution of DZCyt for the target cytosine in G-C-G-C sites in double-stranded oligodeoxyribonucleotides had a similar effect on methylation by M. HhaI. Oligodeoxyribonucleotides containing DZCyt formed a tight but reversible complex with M.HhaI, and were consistently more potent as inhibitors of DNA methylation than oligodeoxyribonucleotides identical in sequence containing 5-fluorocytosine. Crystallographic analysis of a ternary complex involving M.HhaI, S-adenosyl-l-homocysteine and a double-stranded 13-mer oligodeoxyribonucleotide containing DZCyt at the target position showed that the analog is flipped out of the DNA helix in the same manner as cytosine, 5-methylcytosine, and 5-fluorocytosine. However, no formation of a covalent bond was detected between the sulfur atom of the catalytic site nucleophile, cysteine 81, and the pyrimidine C6 carbon. These results indicate that DZCyt can occupy the active site of M.HhaI as a transition state mimic and, because of the high degree of affinity of its interaction with the enzyme, it can act as a potent inhibitor of methylation.


    Organizational Affiliation

    Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha 68198-4525, USA.



Macromolecules

Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 3
MoleculeChainsSequence LengthOrganismDetailsImage
PROTEIN (CYTOSINE-SPECIFIC METHYLTRANSFERASE HHAI)C [auth A]327Haemophilus haemolyticusMutation(s): 0 
EC: 2.1.1.73 (PDB Primary Data), 2.1.1.37 (UniProt)
UniProt
Find proteins for P05102 (Haemophilus parahaemolyticus)
Explore P05102 
Go to UniProtKB:  P05102
Protein Feature View
Expand
  • Reference Sequence
  • Find similar nucleic acids by:  Sequence   |   Structure
  • Entity ID: 1
    MoleculeChainsLengthOrganismImage
    DNA (5'-D(P*CP*CP*AP*TP*GP*(5CM)P*GP*CP*TP*GP*AP*C)-3')A [auth B]12N/A
    Protein Feature View
    Expand
    • Reference Sequence
    • Find similar nucleic acids by:  Sequence   |   Structure
    • Entity ID: 2
      MoleculeChainsLengthOrganismImage
      DNA (5'-D(P*GP*TP*CP*AP*GP*5NCP*GP*CP*AP*TP*GP*G)-3')B [auth C]12N/A
      Protein Feature View
      Expand
      • Reference Sequence
      Small Molecules
      Ligands 1 Unique
      IDChainsName / Formula / InChI Key2D Diagram3D Interactions
      SAH
      Query on SAH

      Download Ideal Coordinates CCD File 
      D [auth A]S-ADENOSYL-L-HOMOCYSTEINE
      C14 H20 N6 O5 S
      ZJUKTBDSGOFHSH-WFMPWKQPSA-N
       Ligand Interaction
      Experimental Data & Validation

      Experimental Data

      • Method: X-RAY DIFFRACTION
      • Resolution: 2.55 Å
      • R-Value Work: 0.205 
      • R-Value Observed: 0.205 
      • Space Group: H 3 2
      Unit Cell:
      Length ( Å )Angle ( ˚ )
      a = 99.86α = 90
      b = 99.86β = 90
      c = 325.2γ = 120
      Software Package:
      Software NamePurpose
      X-PLORrefinement
      DENZOdata reduction
      SCALEPACKdata scaling

      Structure Validation

      View Full Validation Report



      Entry History 

      Deposition Data

      Revision History  (Full details and data files)

      • Version 1.0: 1999-02-09
        Type: Initial release
      • Version 1.1: 2008-04-27
        Changes: Version format compliance
      • Version 1.2: 2011-07-13
        Changes: Version format compliance