2eg5

The structure of xanthosine methyltransferase

spinqualitylabelsall models 2eg5, resolution 2.20Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2eg5 is a 4 chain structure with sequence from Coffea canephora. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.2Å Ligands: SAH, XTS Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function 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 Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. 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 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Dihydroorotase 3D structures

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