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Updated: Aug 20, 2026

Sequence-specific Labeling of Nucleic Acids and Proteins with Methyltransferases and Cofactor Analogues
Published on: November 22, 2014
Cations modulate the substrate specificity of bifunctional class I O-methyltransferase from Ammi majus
Richard Lukacin1, Ulrich Matern, Silvia Specker
1Institut für Pharmazeutische Biologie der Philipps-Universität Marburg, Deutschhausstr. 17A, D- 35037 Marburg/Lahn, Germany.
Abstract:
Caffeoyl-coenzyme A O-methyltransferase cDNA was cloned from dark-grown Ammi majus L. (Apiaceae) cells treated with a crude fungal elicitor and the open reading frame was expressed in Escherichia coli. The translated polypeptide of 27.1-kDa shared significant identity to other members of this highly conserved class of proteins and was 98.8% identical to the corresponding O-methyltransferase from parsley. For biochemical characterization, the recombinant enzyme could be purified to apparent homogeneity by metal-affinity chromatography, although the recombinant enzyme did not contain any affinity tag. Based on sequence analysis and substrate specificity, the enzyme classifies as a cation-dependent O-methyltransferase with pronounced preference for caffeoyl coenzyme A, when assayed in the presence of Mg2+-ions. Surprisingly, however, the substrate specificity changed dramatically, when Mg2+ was replaced by Mn2+ or Co2+ in the assays. This effect could point to yet unknown functions and substrate specificities in situ and suggests promiscuous roles for the lignin specific cluster of plant O-methyltransferases.
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