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2z6u

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[[Image:2z6u.gif|left|200px]]
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{{STRUCTURE_2z6u| PDB=2z6u | SCENE= }}
{{STRUCTURE_2z6u| PDB=2z6u | SCENE= }}
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'''Ternary structure of the Glu119Ala M.HhaI, C5-Cytosine DNA methyltransferase, with unmodified DNA and AdoHcy'''
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===Ternary structure of the Glu119Ala M.HhaI, C5-Cytosine DNA methyltransferase, with unmodified DNA and AdoHcy===
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==Overview==
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The role of Glu119 in S-adenosyl-L-methionine-dependent DNA methyltransferase M.HhaI-catalyzed DNA methylation was studied. Glu119 belongs to the highly conserved Glu/Asn/Val motif found in all DNA C5-cytosine methyltransferases, and its importance for M.HhaI function remains untested. We show that formation of the covalent intermediate between Cys81 and the target cytosine requires Glu119, since conversion to Ala, Asp or Gln lowers the rate of methyl transfer 10(2)-10(6) fold. Further, unlike the wild-type M.HhaI, these mutants are not trapped by the substrate in which the target cytosine is replaced with the mechanism-based inhibitor 5-fluorocytosine. The DNA binding affinity for the Glu119Asp mutant is decreased 10(3)-fold. Thus, the ability of the enzyme to stabilize the extrahelical cytosine is coupled directly to tight DNA binding. The structures of the ternary protein/DNA/AdoHcy complexes for both the Glu119Ala and Glu119Gln mutants (2.70 A and 2.75 A, respectively) show that the flipped base is positioned nearly identically with that observed in the wild-type M.HhaI complex. A single water molecule in the Glu119Ala structure between Ala119 and the extrahelical cytosine N3 is lacking in the Glu119Gln and wild-type M.HhaI structures, and most likely accounts for this mutant's partial activity. Glu119 has essential roles in activating the target cytosine for nucleophilic attack and contributes to tight DNA binding.
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(as it appears on PubMed at http://www.pubmed.gov), where 17897676 is the PubMed ID number.
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{{ABSTRACT_PUBMED_17897676}}
==About this Structure==
==About this Structure==
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[[Category: Transferase]]
[[Category: Transferase]]
[[Category: Transferase/dna complex]]
[[Category: Transferase/dna complex]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 20:00:53 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 14:10:46 2008''

Revision as of 11:10, 27 July 2008

Image:2z6u.png

Template:STRUCTURE 2z6u

Ternary structure of the Glu119Ala M.HhaI, C5-Cytosine DNA methyltransferase, with unmodified DNA and AdoHcy

Template:ABSTRACT PUBMED 17897676

About this Structure

2Z6U is a Protein complex structure of sequences from Haemophilus parahaemolyticus. Full crystallographic information is available from OCA.

Reference

AdoMet-dependent methyl-transfer: Glu119 is essential for DNA C5-cytosine methyltransferase M.HhaI., Shieh FK, Reich NO, J Mol Biol. 2007 Nov 9;373(5):1157-68. Epub 2007 Aug 19. PMID:17897676

Page seeded by OCA on Sun Jul 27 14:10:46 2008

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