title: Comparative structures of the apopolysialoglycoproteins from unfertilized and fertilized eggs of salmonid fishes.
abstract: The complete amino acid sequence of the major polysialoglycoproteins (PSGPs) from two genera of salmonid fish eggs, Salvelinus and Oncorhynchus, has been determined. The occurrence of tandem repeats of a genus-specific dodeca- and tridecapeptide was found for the apoPSGP of Salvelinus leucomaenis pluvius (Slp) and Oncorhynchus masou ishikawai (Omi), respectively, their amino acid sequences being highly homologous with that of rainbow trout [Salmo gairdneri (Sg)] apoPSGP (*denotes the glycosylation site; mean value of N = approximately 25): H-PSGP(Slp): (Asp-Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-)N H-PSGP(Omi): (Asp-Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-Ser-)N H-PSGP(Sg): (Asp-Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-Gly-)N Within 5-7 min following fertilization H-PSGP is converted to the low-molecular-mass PSGP (L-PSGP) by a specific protease (PSGPase). We have purified L-PSGP from the fertilized eggs of S. leucomaenis pluvius and Oncorhynchus keta (chum salmon) and compared it with rainbow trout egg L-PSGP(Sg) by analysis of their amino acid sequence: L-PSGP(Slp): Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-Asp L-PSGP(Ok): Asp-Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-Ser L-PSGP(Sg): Asp-Asp-Ala-Thr*-Ser*-Glu-Ala-Ala-Thr*-Gly-Pro-Ser-Gly The data support the conclusion that H-PSGP is degraded in vivo 5-7 min after fertilization to L-PSGP by proteolytic cleavage at the position two residues C-terminally to the Pro residue, i.e., -Pro-Ser-Xaa-Asp-(Xaa = either Gly, Ser, or Asp) by the action of PSGPase.
authors.affiliation: Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kitajima
authors.forename: H
authors.initials: H
authors.lastname: Sorimachi
authors.forename: S
authors.initials: S
authors.lastname: Inoue
authors.forename: Y
authors.initials: Y
authors.lastname: Inoue
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001059:Apoproteins / Q000302:isolation & purification; D008969:Molecular Sequence Data; D010063:Ovum / Q000032:analysis; D012487:Salmonidae / Q000378:metabolism*; D012795:Sialoglycoproteins; D013045:Species Specificity; D015053:Zygote / Q000032:analysis
chemical_list: D001059:Apoproteins; D012795:Sialoglycoproteins; C057821:apopolysialoglycoprotein, salmonid fish eggs