title: Phosphorylation of SUMO-1 occurs in vivo and is conserved through evolution.
abstract: Protein dynamics is regulated by an elaborate interplay between different post-translational modifications. Ubiquitin and ubiquitin-like proteins (Ubls) are small proteins that are covalently conjugated to target proteins with important functional consequences. One such modifier is SUMO, which mainly modifies nuclear proteins. SUMO contains a unique N-terminal arm not present in ubiquitin and other Ubls, which functions in the formation of SUMO polymers. Here, we unambiguously show that serine 2 of the endogenous SUMO-1 N-terminal protrusion is phosphorylated in vivo using very high mass accuracy mass spectrometry at both the MS and the MS/MS level and complementary fragmentation techniques. Strikingly, we detected the same phosphorylation in yeast, Drosophila and human cells, suggesting an evolutionary conserved function for this modification. The nearly identical human SUMO-2 and SUMO-3 isoforms differ in serine 2; thus, only SUMO-3 could be phosphorylated at this position. Our finding that SUMO can be modified may point to an additional level of complexity through modifying a protein-modifier.
authors.affiliation: Department of Proteomics and Signal Transduction, Max Planck Institute for Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany.
authors.forename: Ivan
authors.initials: I
authors.lastname: Matic
authors.forename: Boris
authors.initials: B
authors.lastname: Macek
authors.forename: Maximiliane
authors.initials: M
authors.lastname: Hilger
authors.forename: Tobias C
authors.initials: TC
authors.lastname: Walther
authors.forename: Matthias
authors.initials: M
authors.lastname: Mann
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019143:Evolution, Molecular; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation; D025842:SUMO-1 Protein / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D053719:Tandem Mass Spectrometry
chemical_list: D025842:SUMO-1 Protein