title: Identification and validation of eukaryotic aspartate and glutamate methylation in proteins.
abstract: Methylation of lysine and arginine is known to be critical in cellular processes. However, methylation of other amino acidic residues has been largely overlooked. Here, we report a systematic screening for methylation of side chains of aspartate and glutamate (D/E-methylation), involving exhaustive nano-HPLC/MS/MS, a protein sequence database search, and manual verification. The putative D/E-methylated peptides were confirmed by MS/MS of synthetic peptides. Our analysis identified several D/E-methylation substrate proteins and their modification sites in human and yeast cells. To our knowledge, this is the first report conclusively identifying in vivo D/E-methylation substrates and their modification sites in eukaryotic cells, demonstrating that D/E-methylations are abundant protein modifications. The substrate proteins identified here provide a stepping stone for future biochemical characterization of protein methylation pathways.
authors.affiliation: Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9038, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Sprung
authors.forename: Yue
authors.initials: Y
authors.lastname: Chen
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.forename: Dongmei
authors.initials: D
authors.lastname: Cheng
authors.forename: Terry
authors.initials: T
authors.lastname: Zhang
authors.forename: Junmin
authors.initials: J
authors.lastname: Peng
authors.forename: Yingming
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D000595:Amino Acid Sequence; D001224:Aspartic Acid / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008745:Methylation; D008969:Molecular Sequence Data; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D040901:Proteomics; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D053719:Tandem Mass Spectrometry
chemical_list: D011506:Proteins; D001224:Aspartic Acid; D018698:Glutamic Acid