Biological Assembly 1  

 3D View: Structure | 1D-3D View | Validation Report | Ligand Interaction

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Monomer - A1 

Biological assembly 1 assigned by authors.

Macromolecule Content

• Total Structure Weight: 44.77 kDa 
• Atom Count: 3237 
• Modelled Residue Count: 351 
• Deposited Residue Count: 351 
• Unique protein chains: 1
• Unique nucleic acid chains: 2

5MHT

TERNARY STRUCTURE OF HHAI METHYLTRANSFERASE WITH HEMIMETHYLATED DNA AND ADOHCY

• PDB DOI: 10.2210/pdb5MHT/pdb

• Classification: TRANSFERASE/DNA
• Organism(s): Haemophilus haemolyticus
• Mutation(s): No 


• Deposited: 1996-10-22 Released: 1997-07-23 
• Deposition Author(s): Cheng, X.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 2.70 Å
• R-Value Work: 0.188 
• R-Value Observed: 0.188 

Literature

A structural basis for the preferential binding of hemimethylated DNA by HhaI DNA methyltransferase.

O'Gara, M., Roberts, R.J., Cheng, X.

(1996) J Mol Biol 263: 597-606

• PubMed: 8918941 
• DOI: 10.1006/jmbi.1996.0601
• Primary Citation of Related Structures:  
  5MHT


• PubMed Abstract: 
  

The crystal structure of HhaI methyltransferase complexed with non-palindromic duplex DNA, containing a hemimethylated recognition sequence, and with the cofactor analog S-adenosyl-L-homocysteine (AdoHcy), has been determined. The structure provides an explanation for the stronger affinities of DNA methyltransferases for hemimethylated DNA than for unmethylated or fully methylated DNA in the presence of AdoHcy. The unmethylated target 2'-deoxycytidine flips out of the DNA helix and the CH group at position 5 makes van der Waals' contacts with the sulfur atom of AdoHcy. Selectivity/preference for hemimethylated over fully methylated DNA may thus reflect interactions among the chemical substituent (H or CH3) at the C5 position of the flipped cytosine, protein and the bound AdoHcy. The 5-methyl-2'-deoxycytidine on the complementary strand remains in the DNA helix, with the methyl group almost perpendicular to the carboxylate group of Glu239, which is part of the sequence recognition loop. Thus, selectivity/preference for hemimethylated over unmethylated DNA appears to result largely from van der Waals' contacts between the planar Glu239 carboxylate and the methyl group of the 5-methyl-2'-deoxycytidine. Furthermore, the positive electrostatic potential originating from the bound AdoHcy extends to the DNA phosphate groups flanking the flipped cytosine. The increased binding to DNA by long-range electrostatic interactions should also occur with the methyl donor S-adenosyl-L-methionine.

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Related Citations: 

• Enzymatic C5-Cytosine Methylation of DNA: Mechanistic Implications of New Crystal Structures for HhaI Methyltransferase-DNA-Adohcy Complexes
  O'Gara, M., Klimasauskas, S., Roberts, R.J., Cheng, X.
  (1996) J Mol Biol 261: 634

• HhaI Methyltransferase Flips its Target Base Out of the DNA Helix
  Klimasauskas, S., Kumar, S., Roberts, R.J., Cheng, X.
  (1994) Cell 76: 357

• Crystal Structure of the HhaI DNA Methyltransferase Complexed with S-Adenosyl- L-Methionine
  Cheng, X., Kumar, S., Posfai, J., Pflugrath, J.W., Roberts, R.J.
  (1993) Cell 74: 299

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Organizational Affiliation: 

W.M. Keck Structural Biology Laboratory, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.

Macromolecules

Entity ID: 3
Molecule	Chains	Sequence Length	Organism	Details	Image
PROTEIN (HHAI METHYLTRANSFERASE)	C [auth A]	327	Haemophilus haemolyticus	Mutation(s): 0  EC: 2.1.1.7 (PDB Primary Data), 2.1.1.37 (UniProt)
UniProt
Find proteins for P05102 (Haemophilus parahaemolyticus) Explore P05102  Go to UniProtKB:  P05102

Entity ID: 1
Molecule	Chains	Length	Organism	Image
DNA (5'-D(*CP*CP*AP*TP*GP*(5CM)P*GP*CP*TP*GP*AP*C)-3')	A [auth C]	12	N/A

Entity ID: 2
Molecule	Chains	Length	Organism	Image
DNA (5'-D(*GP*TP*CP*AP*GP*CP*GP*CP*AP*TP*GP*G)-3')	B [auth D]	12	N/A

Small Molecules

Ligands 1 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
SAH	D [auth A]	S-ADENOSYL-L-HOMOCYSTEINE C14 H20 N6 O5 S ZJUKTBDSGOFHSH-WFMPWKQPSA-N

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 2.70 Å
• R-Value Work: 0.188 
• R-Value Observed: 0.188 
• Space Group: H 3 2

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 99.86	α = 90
b = 99.86	β = 90
c = 325.2	γ = 120

Software Package:

Software Name	Purpose
X-PLOR	refinement
DENZO	data reduction
SCALEPACK	data scaling

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 1996-10-22 
• Released Date: 1997-07-23 
Deposition Author(s): Cheng, X.

Revision History  

• Version 1.0: 1997-07-23
  Type: Initial release
  
• Version 1.1: 2008-05-22
  Changes: Version format compliance
• Version 1.2: 2011-07-13
  Changes: Version format compliance