title: Localization of labile posttranslational modifications by electron capture dissociation: the case of gamma-carboxyglutamic acid.
abstract: Tandem mass spectrometry (MS/MS) of 28 residue peptides harboring gamma-carboxylated glutamic acid residues, a posttranslational modification of several proenzymes of the blood coagulation cascade, using either collisions or infrared photons results in complete ejection of the gamma-CO2 moieties (-44 Da) before cleavage of peptide-backbone bonds. However, MS/MS using electron capture dissociation (ECD) in a Fourier transform mass spectrometer cleaves backbone bonds without ejecting CO2, allowing direct localization of this labile modification. Sulfated side chains are also retained in ECD backbone fragmentations of a 21-mer peptide, although CAD causes extensive SO3 loss. ECD thus is a unique complement to conventional methods for MS/MS, causing less undesirable loss of side-chain functionalities as well as more desirable backbone cleavages.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: N L
authors.initials: NL
authors.lastname: Kelleher
authors.forename: R A
authors.initials: RA
authors.lastname: Zubarev
authors.forename: K
authors.initials: K
authors.lastname: Bush
authors.forename: B
authors.initials: B
authors.lastname: Furie
authors.forename: B C
authors.initials: BC
authors.lastname: Furie
authors.forename: F W
authors.initials: FW
authors.lastname: McLafferty
authors.forename: C T
authors.initials: CT
authors.lastname: Walsh
mesh_terms: D015055:1-Carboxyglutamic Acid / Q000032:analysis* / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D007477:Ions; D013058:Mass Spectrometry / Q000379:methods*; D008969:Molecular Sequence Data; D010455:Peptides / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D013431:Sulfates
chemical_list: D007477:Ions; D010455:Peptides; D013431:Sulfates; D015055:1-Carboxyglutamic Acid