title: O-linked fucose is present in the first epidermal growth factor domain of factor XII but not protein C.
abstract: Epidermal growth factor (EGF) domains are found in many proteins, particularly those of the coagulation/fibrinolytic system. We and others have demonstrated that tissue plasminogen activator (t-PA) and prourokinase are modified by the attachment of fucose to equivalent threonine residues within their EGF domains. Factor XII and protein C each contain two EGF domains; in both proteins, the EGF domain nearest the N terminus has a threonine residue in a position homologous to that which is fucosylated in t-PA. In protein C, this site is 3 residues from the position of another post-translational modification, beta-hydroxylation of Asp-71. We isolated peptides containing these sites to determine, primarily by mass spectrometric analysis, the presence of O-linked fucose and/or beta-hydroxyaspartate. We found that factor XII is fully fucosylated at Thr-90. Protein C is unmodified at the equivalent site (Thr-68) and is completely beta-hydroxylated at Asp-71. It has been recently reported that the first EGF domain of human factor VII has O-linked fucose at the equivalent position (Ser-60) (Bjoern, S., Foster, D. C., Thim, L., Wiberg, F. C., Christensen, M., Komiyama, Y., Pedersen, A. H., and Kisiel, W. (1991) J. Biol. Chem. 266, 11051-11057), while it is unmodified at Asp-63 despite having the consensus sequence for beta-hydroxylation at the latter site. These observations raise the possibility that O-linked fucosylation and beta-hydroxylation of EGF domains are mutually exclusive post-translational modifications.
authors.affiliation: Department of Medicinal and Analytical Chemistry, Genentech Inc., South San Francisco, California 94080.
authors.forename: R J
authors.initials: RJ
authors.lastname: Harris
authors.forename: V T
authors.initials: VT
authors.lastname: Ling
authors.forename: M W
authors.initials: MW
authors.lastname: Spellman
mesh_terms: D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid; D003488:Cyanogen Bromide; D004815:Epidermal Growth Factor / Q000737:chemistry*; D005174:Factor XII / Q000737:chemistry*; D005643:Fucose / Q000032:analysis*; D006801:Humans; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000302:isolation & purification; D010449:Peptide Mapping; D011486:Protein C / Q000737:chemistry*; D012689:Sequence Homology, Nucleic Acid
chemical_list: D010446:Peptide Fragments; D011486:Protein C; D005643:Fucose; D004815:Epidermal Growth Factor; D005174:Factor XII; D003488:Cyanogen Bromide