Identification and validation of eukaryotic aspartate and glutamate methylation in proteins.
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.
Sprung
Robert
R
Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9038, USA.
Chen
Yue
Y
Zhang
Kai
K
Cheng
Dongmei
D
Zhang
Terry
T
Peng
Junmin
J
Zhao
Yingming
Y
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
D011506:Proteins; D001224:Aspartic Acid; D018698:Glutamic Acid