View source for 2eg5


==The structure of xanthosine methyltransferase==
<StructureSection load='2eg5' size='340' side='right'caption='[[2eg5]], [[Resolution|resolution]] 2.20&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[2eg5]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Coffea_canephora Coffea canephora]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2EG5 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2EG5 FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.2&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=SAH:S-ADENOSYL-L-HOMOCYSTEINE'>SAH</scene>, <scene name='pdbligand=XTS:9-[(2R,3R,4S,5R)-3,4-DIHYDROXY-5-(HYDROXYMETHYL)OXOLAN-2-YL]-3H-PURINE-2,6-DIONE'>XTS</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=2eg5 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2eg5 OCA], [https://pdbe.org/2eg5 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2eg5 RCSB], [https://www.ebi.ac.uk/pdbsum/2eg5 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2eg5 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/XMT1_COFCA XMT1_COFCA] Involved in the biosynthesis of caffeine. Specific for xanthosine. Cannot use xanthosine 5'-monophosphate (XMP) as substrate. Directly produces 7-methylxanthine, and therefore the methyl transfer and nucleoside cleavage may be coupled. Catalyzes the 7-N-methylation of xanthosine, but does not have 1-N- or 3-N-methylation activity.
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/eg/2eg5_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=2eg5 ConSurf].
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== Publication Abstract from PubMed ==
Caffeine (1,3,7-trimethylxanthine) is a secondary metabolite produced by certain plant species and an important component of coffee (Coffea arabica and Coffea canephora) and tea (Camellia sinensis). Here we describe the structures of two S-adenosyl-l-methionine-dependent N-methyltransferases that mediate caffeine biosynthesis in C. canephora 'robusta', xanthosine (XR) methyltransferase (XMT), and 1,7-dimethylxanthine methyltransferase (DXMT). Both were cocrystallized with the demethylated cofactor, S-adenosyl-L-cysteine, and substrate, either xanthosine or theobromine. Our structures reveal several elements that appear critical for substrate selectivity. Serine-316 in XMT appears central to the recognition of XR. Likewise, a change from glutamine-161 in XMT to histidine-160 in DXMT is likely to have catalytic consequences. A phenylalanine-266 to isoleucine-266 change in DXMT is also likely to be crucial for the discrimination between mono and dimethyl transferases in coffee. These key residues are probably functionally important and will guide future studies with implications for the biosynthesis of caffeine and its derivatives in plants.

The structure of two N-methyltransferases from the caffeine biosynthetic pathway.,McCarthy AA, McCarthy JG Plant Physiol. 2007 Jun;144(2):879-89. Epub 2007 Apr 13. PMID:17434991<ref>PMID:17434991</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 2eg5" style="background-color:#fffaf0;"></div>

==See Also==
*[[Dihydroorotase 3D structures|Dihydroorotase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Coffea canephora]]
[[Category: Large Structures]]
[[Category: McCarthy AA]]
[[Category: McCarthy JG]]