title: Isolation and partial characterization of a pentraxin-like protein with complement-fixing activity from snapper (Pagrus auratus, Sparidae) serum.
abstract: Pentraxin-like molecules have been isolated from a number of fish species. However, little is known about the function of these proteins in the teleosts. In this study we report the isolation and characterization of a pentraxin-like molecule from the serum of snapper (Pagrus auratus) that has the ability to activate complement. This pentraxin-like protein was isolated from serum by calcium-dependent binding to agarose. SDS-PAGE analysis demonstrated an oligomeric protein of approximately 200k Da consisting of non-covalently bound subunits of 26 and 23 kDa. Protein sequencing revealed significant (50%) sequence identity with pentraxins from both Atlantic salmon (S. salar) and rainbow trout (O. mykiss). However, polyclonal antibodies raised against snapper pentraxin did not recognise salmon or trout pentraxin in Western blot analysis. Following LPS injection, snapper pentraxin levels increased 2-fold before gradually returning to basal levels. Most significantly, the isolated pentraxin initiated complement-mediated lysis of ligand-coated sheep erythrocytes in a dose-dependent fashion. In view of the similarity between the known fish pentraxins, and their similarity to mammalian serum amyloid P-components we conclude that the isolated protein may be a snapper pentraxin homologue.
authors.affiliation: Dame Roma Mitchell Cancer Research Laboratories, Hanson Institute, Institute of Medical and Veterinary Science, Frome Road, Adelaide, SA 5000, Australia.
authors.forename: Mathew T
authors.initials: MT
authors.lastname: Cook
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hayball
authors.forename: Laurie
authors.initials: L
authors.lastname: Birdseye
authors.forename: Christopher
authors.initials: C
authors.lastname: Bagley
authors.forename: Barbara F
authors.initials: BF
authors.lastname: Nowak
authors.forename: John D
authors.initials: JD
authors.lastname: Hayball
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002097:C-Reactive Protein / Q000235:genetics* / Q000378:metabolism; D003165:Complement System Proteins / Q000378:metabolism*; D005399:Fishes / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family; D000683:Serum Amyloid P-Component / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D000683:Serum Amyloid P-Component; D003165:Complement System Proteins; D002097:C-Reactive Protein