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Acta Crystallogr Sect F Struct Biol Cryst Commun. 2007 Apr 1;63(Pt 4):304-7. Epub 2007 Mar 12.

Cloning, expression, crystallization and preliminary X-ray analysis of the XMT and DXMT N-methyltransferases from Coffea canephora (robusta).

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European Molecular Biology Laboratory, 6 Rue Jules Horowitz, BP 181, 38042 Grenoble, France.


Caffeine is a secondary metabolite produced by a variety of plants including Coffea canephora (robusta) and there is growing evidence that caffeine is part of a chemical defence strategy protecting young leaves and seeds from potential predators. The genes encoding XMT and DXMT, the enzymes from Coffea canephora (robusta) that catalyse the three independent N-methyl transfer reactions in the caffeine-biosynthesis pathway, have been cloned and the proteins have been expressed in Escherichia coli. Both proteins have been crystallized in the presence of the demethylated cofactor S-adenosyl-L-cysteine (SAH) and substrate (xanthosine for XMT and theobromine for DXMT). The crystals are orthorhombic, with space group P2(1)2(1)2(1) for XMT and C222(1) for DXMT. X-ray diffraction to 2.8 A for XMT and to 2.5 A for DXMT have been collected on beamline ID23-1 at the ESRF.

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