O-carboxyl- and N-methyltransferases active on plant aquaporins.
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 K(m) 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.
Biochimie et Physiologie Moléculaire des Plantes, Institut de Biologie Intégrative des plantes, UMR 5004 CNRS/UMR 0386 INRA/Montpellier SupAgro/Université Montpellier 2, F-34060 Montpellier Cedex 2, France.
Tobias
T
Sahr
Thibaud
T
Adam
Cécile
C
Fizames
Christophe
C
Maurel
Véronique
V
Santoni
D000595:Amino Acid Sequence; D020346:Aquaporins / Q000737:chemistry / Q000378:metabolism; D017360:Arabidopsis / Q000737:chemistry / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D008745:Methylation; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D010802:Phylogeny; D030821:Plants, Genetically Modified / Q000737:chemistry / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D011496:Protein Methyltransferases / Q000235:genetics / Q000378:metabolism*; D011497:Protein O-Methyltransferase / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000737:chemistry; D013379:Substrate Specificity
D020346:Aquaporins; D029681:Arabidopsis Proteins; D010455:Peptides; D011994:Recombinant Proteins; C491680:plasma membrane intrinsic protein 2 Arabidopsis; D012436:S-Adenosylmethionine; D011496:Protein Methyltransferases; D011497:Protein O-Methyltransferase