1mht
From Proteopedia
(New page: 200px<br /><applet load="1mht" size="450" color="white" frame="true" align="right" spinBox="true" caption="1mht, resolution 2.60Å" /> '''COVALENT TERNARY STR...) |
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| - | [[Image:1mht.jpg|left|200px]]<br /><applet load="1mht" size=" | + | [[Image:1mht.jpg|left|200px]]<br /><applet load="1mht" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1mht, resolution 2.60Å" /> | caption="1mht, resolution 2.60Å" /> | ||
'''COVALENT TERNARY STRUCTURE OF HHAI METHYLTRANSFERASE, DNA AND S-ADENOSYL-L-HOMOCYSTEINE'''<br /> | '''COVALENT TERNARY STRUCTURE OF HHAI METHYLTRANSFERASE, DNA AND S-ADENOSYL-L-HOMOCYSTEINE'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The crystal structure has been determined at 2.8 A resolution for a | + | The crystal structure has been determined at 2.8 A resolution for a chemically-trapped covalent reaction intermediate between the HhaI DNA cytosine-5-methyltransferase, S-adenosyl-L-homocysteine, and a duplex 13-mer DNA oligonucleotide containing methylated 5-fluorocytosine at its target. The DNA is located in a cleft between the two domains of the protein and has the characteristic conformation of B-form DNA, except for a disrupted G-C base pair that contains the target cytosine. The cytosine residue has swung completely out of the DNA helix and is positioned in the active site, which itself has undergone a large conformational change. The DNA is contacted from both the major and the minor grooves, but almost all base-specific interactions between the enzyme and the recognition bases occur in the major groove, through two glycine-rich loops from the small domain. The structure suggests how the active nucleophile reaches its target, directly supports the proposed mechanism for cytosine-5 DNA methylation, and illustrates a novel mode of sequence-specific DNA recognition. |
==About this Structure== | ==About this Structure== | ||
| - | 1MHT is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Haemophilus_haemolyticus Haemophilus haemolyticus] with SAH as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Deleted_entry Deleted entry], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.1.1.73 2.1.1.73] Full crystallographic information is available from [http:// | + | 1MHT is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Haemophilus_haemolyticus Haemophilus haemolyticus] with <scene name='pdbligand=SAH:'>SAH</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Deleted_entry Deleted entry], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.1.1.73 2.1.1.73] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1MHT OCA]. |
==Reference== | ==Reference== | ||
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[[Category: protein-dna complex]] | [[Category: protein-dna complex]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:55:23 2008'' |
Revision as of 11:55, 21 February 2008
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COVALENT TERNARY STRUCTURE OF HHAI METHYLTRANSFERASE, DNA AND S-ADENOSYL-L-HOMOCYSTEINE
Overview
The crystal structure has been determined at 2.8 A resolution for a chemically-trapped covalent reaction intermediate between the HhaI DNA cytosine-5-methyltransferase, S-adenosyl-L-homocysteine, and a duplex 13-mer DNA oligonucleotide containing methylated 5-fluorocytosine at its target. The DNA is located in a cleft between the two domains of the protein and has the characteristic conformation of B-form DNA, except for a disrupted G-C base pair that contains the target cytosine. The cytosine residue has swung completely out of the DNA helix and is positioned in the active site, which itself has undergone a large conformational change. The DNA is contacted from both the major and the minor grooves, but almost all base-specific interactions between the enzyme and the recognition bases occur in the major groove, through two glycine-rich loops from the small domain. The structure suggests how the active nucleophile reaches its target, directly supports the proposed mechanism for cytosine-5 DNA methylation, and illustrates a novel mode of sequence-specific DNA recognition.
About this Structure
1MHT is a Single protein structure of sequence from Haemophilus haemolyticus with as ligand. Active as Deleted entry, with EC number 2.1.1.73 Full crystallographic information is available from OCA.
Reference
HhaI methyltransferase flips its target base out of the DNA helix., Klimasauskas S, Kumar S, Roberts RJ, Cheng X, Cell. 1994 Jan 28;76(2):357-69. PMID:8293469
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