title: Improved mass spectrometric characterization of protein glycosylation reveals unusual glycosylation of maize-derived bovine trypsin.
abstract: Although bottom-up proteomics using tryptic digests is widely used to locate post-translational modifications (PTM) in proteins, there are cases where the protein has several potential modification sites within a tryptic fragment and MS(2) strategies fail to pinpoint the location. We report here a method using two proteolytic enzymes, trypsin and pepsin, in combination followed by tandem mass spectrometric analysis to provide fragments that allow one to locate the modification sites. We used this strategy to find a glycosylation site on bovine trypsin expressed in maize (TrypZean). Several glycans are present, and all are attached to a nonconsensus N-glycosylation site on the protein.
authors.affiliation: Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States.
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Richard Y C
authors.initials: RY
authors.lastname: Huang
authors.forename: Pegah R
authors.initials: PR
authors.lastname: Jalili
authors.forename: Janet W
authors.initials: JW
authors.lastname: Irungu
authors.forename: Gordon R
authors.initials: GR
authors.lastname: Nicol
authors.forename: Kevin B
authors.initials: KB
authors.lastname: Ray
authors.forename: Henry W
authors.initials: HW
authors.lastname: Rohrs
authors.forename: Michael L
authors.initials: ML
authors.lastname: Gross
mesh_terms: D000818:Animals; D002417:Cattle; D006031:Glycosylation; D010434:Pepsin A / Q000378:metabolism; D010446:Peptide Fragments / Q000032:analysis*; D011499:Protein Processing, Post-Translational; D040901:Proteomics / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014357:Trypsin / Q000032:analysis / Q000378:metabolism*; D003313:Zea mays / Q000378:metabolism*
chemical_list: D010446:Peptide Fragments; D014357:Trypsin; D010434:Pepsin A