Journal Article

<i>O</i>-Carboxyl- and <i>N</i>-Methyltransferases Active on Plant Aquaporins

Tobias Sahr, Thibaud Adam, Cécile Fizames, Christophe Maurel and Véronique Santoni

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 51, issue 12, pages 2092-2104
Published in print December 2010 | ISSN: 0032-0781
Published online November 2010 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcq171
O-Carboxyl- and N-Methyltransferases Active on Plant Aquaporins

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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Methylation of biologically active molecules is achieved by methyltransferases (MTases). MTases can act on proteins through N- or O-carboxylmethylation reactions. Methylation of lysine and glutamic acid residues was recently described on the N-terminal tail of AtPIP2;1, a plasma membrane aquaporin of plants. In this study, we combine a bioinformatic and a biochemical screen and identify two MTases of Arabidopsis thaliana, SDG7 (At2g44150) and OMTF3 (At3g61990), as acting on the N-terminal tail of AtPIP2;1, at Lys3 and Glu6, respectively. Confocal microscopy imaging showed the two enzymes to be associated with the endoplasmic reticulum. An in vitro assay using various AtPIP2;1 N-terminal peptides as a bait allowed characterization of the enzymatic properties of recombinant SDG7 and OMTF3. The two enzymes showed minimal apparent Km values for their substrates, S-adenosylmethionine and peptide, in the range of 5–8 and 2–9 μM, respectively. SDG7 was shown to almost exclusively mono- or di-methylate Lys3. In contrast, OMTF3 specifically methylated Glu6, this methylation being dependent on the methylation profile of the neighboring Lys3 residue. In conclusion, this study allows the characterization of the first MTases able to methylate plant transmembrane proteins and provides the first identification of a glutamate-MTase in eukaryotes.

Keywords: Aquaporin; O-Carboxyl-methyltransferase; N-Methyltransferase

Journal Article.  6942 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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