2eg5: Difference between revisions

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-[[Image:2eg5.jpg|left|200px]]
+{{Seed}}
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 {{STRUCTURE_2eg5|  PDB=2eg5  |  SCENE=  }}
-'''The structure of xanthosine methyltransferase'''
+===The structure of xanthosine methyltransferase===
-==Overview==
+<!--
-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 line below this paragraph, {{ABSTRACT_PUBMED_17434991}}, adds the Publication Abstract to the page
+(as it appears on PubMed at http://www.pubmed.gov), where 17434991 is the PubMed ID number.
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+{{ABSTRACT_PUBMED_17434991}}
 ==About this Structure==
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 ==Reference==
 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:[http://www.ncbi.nlm.nih.gov/pubmed/17434991 17434991]
+Cloning, expression, crystallization and preliminary X-ray analysis of the XMT and DXMT N-methyltransferases from Coffea canephora (robusta)., McCarthy AA, Biget L, Lin C, Petiard V, Tanksley SD, McCarthy JG, Acta Crystallogr Sect F Struct Biol Cryst Commun. 2007 Apr 1;63(Pt, 4):304-7. Epub 2007 Mar 12. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/17401201 17401201]
 [[Category: Coffea canephora]]
 [[Category: Single protein]]
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 [[Category: Sam-dependant n-methyltransferase]]
 [[Category: Xanthosine]]
-''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May  4 02:30:03 2008''
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 14:04:32 2008''