1nv9
From Proteopedia
(New page: 200px<br /><applet load="1nv9" size="450" color="white" frame="true" align="right" spinBox="true" caption="1nv9, resolution 2.356Å" /> '''HemK, apo structure...) |
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| - | [[Image:1nv9.gif|left|200px]]<br /><applet load="1nv9" size=" | + | [[Image:1nv9.gif|left|200px]]<br /><applet load="1nv9" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1nv9, resolution 2.356Å" /> | caption="1nv9, resolution 2.356Å" /> | ||
'''HemK, apo structure'''<br /> | '''HemK, apo structure'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Posttranslational methylation of release factors on the glutamine residue | + | Posttranslational methylation of release factors on the glutamine residue of a conserved GGQ motif is required for efficient termination of protein synthesis. This methylation is performed by an N(5)-glutamine methyltransferase called PrmC/HemK, whose crystal structure we report here at 2.2 A resolution. The electron density at the active site appears to contain a mixture of the substrates, S-adenosyl-L-methionine (AdoMet) and glutamine, and the products, S-adenosyl-L-homocysteine (AdoHcy) and N(5)-methylglutamine. The C-terminal domain of PrmC adopts the canonical AdoMet-dependent methyltransferase fold and shares structural similarity with the nucleotide N-methyltransferases in the active site, including use of a conserved (D/N)PPY motif to select and position the glutamine substrate. Residues of the PrmC (197)NPPY(200) motif form hydrogen bonds that position the planar Gln side chain such that the lone-pair electrons on the nitrogen nucleophile are oriented toward the methyl group of AdoMet. In the product complex, the methyl group remains pointing toward the sulfur, consistent with either an sp(3)-hybridized, positively charged Gln nitrogen, or a neutral sp(2)-hybridized nitrogen in a strained conformation. Due to steric overlap within the active site, proton loss and formation of the neutral planar methylamide product are likely to occur during or after product release. These structures, therefore, represent intermediates along the catalytic pathway of PrmC and show how the (D/N)PPY motif can be used to select a wide variety substrates. |
==About this Structure== | ==About this Structure== | ||
| - | 1NV9 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Thermotoga_maritima Thermotoga maritima] with SAH as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http:// | + | 1NV9 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Thermotoga_maritima Thermotoga maritima] with <scene name='pdbligand=SAH:'>SAH</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1NV9 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Thermotoga maritima]] | [[Category: Thermotoga maritima]] | ||
| - | [[Category: Hill, C | + | [[Category: Hill, C P.]] |
| - | [[Category: Phillips, J | + | [[Category: Phillips, J D.]] |
| - | [[Category: Schubert, H | + | [[Category: Schubert, H L.]] |
[[Category: SAH]] | [[Category: SAH]] | ||
[[Category: class i methyltransferase fold]] | [[Category: class i methyltransferase fold]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:10:26 2008'' |
Revision as of 12:10, 21 February 2008
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HemK, apo structure
Overview
Posttranslational methylation of release factors on the glutamine residue of a conserved GGQ motif is required for efficient termination of protein synthesis. This methylation is performed by an N(5)-glutamine methyltransferase called PrmC/HemK, whose crystal structure we report here at 2.2 A resolution. The electron density at the active site appears to contain a mixture of the substrates, S-adenosyl-L-methionine (AdoMet) and glutamine, and the products, S-adenosyl-L-homocysteine (AdoHcy) and N(5)-methylglutamine. The C-terminal domain of PrmC adopts the canonical AdoMet-dependent methyltransferase fold and shares structural similarity with the nucleotide N-methyltransferases in the active site, including use of a conserved (D/N)PPY motif to select and position the glutamine substrate. Residues of the PrmC (197)NPPY(200) motif form hydrogen bonds that position the planar Gln side chain such that the lone-pair electrons on the nitrogen nucleophile are oriented toward the methyl group of AdoMet. In the product complex, the methyl group remains pointing toward the sulfur, consistent with either an sp(3)-hybridized, positively charged Gln nitrogen, or a neutral sp(2)-hybridized nitrogen in a strained conformation. Due to steric overlap within the active site, proton loss and formation of the neutral planar methylamide product are likely to occur during or after product release. These structures, therefore, represent intermediates along the catalytic pathway of PrmC and show how the (D/N)PPY motif can be used to select a wide variety substrates.
About this Structure
1NV9 is a Single protein structure of sequence from Thermotoga maritima with as ligand. Full crystallographic information is available from OCA.
Reference
Structures along the catalytic pathway of PrmC/HemK, an N5-glutamine AdoMet-dependent methyltransferase., Schubert HL, Phillips JD, Hill CP, Biochemistry. 2003 May 20;42(19):5592-9. PMID:12741815
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