title: Purification and characterization of equine complement factor C3.
abstract: A rapid method for purifying equine C3 which yields milligram quantities of pure C3 is described. Protein from equine plasma was selectively precipitated with polyethylene glycol, and the C3 was purified by anionic and cationic exchange HPLC. The yield from this procedure was 12%. The purified C3 was composed of an alpha chain (118 kD) and a beta chain (68 kD) linked by at least one disulfide bond, and it had an isoelectric point of 4.7. Amino acid analysis indicated a strong conservation of amino acid usage between equine and human C3. The N-terminal sequences of the alpha and beta chains were homologous to human, mouse, and rat C3, and activation of C3 produced breakdown products similar in molecular weight to C3b and iC3b of other species. Equine C3 appeared to be functionally dependent upon a reactive thiolester as treatment of fresh equine serum with methylamine abrogated its hemolytic activity.
authors.affiliation: Department of Veterinary Microbiology, Immunology, and Parasitology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.
authors.forename: J S
authors.initials: JS
authors.lastname: Boschwitz
authors.forename: J F
authors.initials: JF
authors.lastname: Timoney
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D003176:Complement C3 / Q000302:isolation & purification*; D006736:Horses / Q000276:immunology*; D006801:Humans; D008969:Molecular Sequence Data; D008970:Molecular Weight; D017386:Sequence Homology, Amino Acid; D012756:Sheep; D013329:Structure-Activity Relationship
chemical_list: D000596:Amino Acids; D003176:Complement C3