Identification and characterization of a variant of the third component of complement (C3) in rainbow trout (Salmo gairdneri) serum.
A rainbow trout serum protein that is cross-reactive with the third complement component of rainbow trout (C3-1) was purified to homogeneity and its structural and functional properties compared with those of C3-1. This protein (termed C3-related protein: C3-2) bears a close structural resemblance to C3-1, although C3-2 apparently shows no hemolytic activity. Like C3-1, C3-2 consists of two disulfide-linked polypeptide chains (128,000 alpha and 72,000 beta) and retains the unique thiol ester site in the alpha-chain. C3-2 shares some antigenicity with C3-1, but it also displays distinctive antigenic determinants of its own. Comparison of tryptic peptide maps revealed that about 20% of the peptides was specific to either C3-1 or C3-2, and about 80% of the peptides were common to both proteins. Amino acid compositions of the alpha- and beta-chains of C3-2 were similar to those of C3-1. Furthermore, amino acid sequence analysis of the NH2 termini of the alpha- and beta-chains of C3-2 revealed a high degree of homology with those of C3-1, 24 of 26 residues in the alpha-chain and all 20 in the beta-chain of C3-2 were identical with those found in C3-1. Both C3-1 and C3-2 were detected in all the adult rainbow trout tested and in first generation offspring randomly bred from them.
D000483:Alleles; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001798:Blood Proteins / Q000032:analysis; D003176:Complement C3 / Q000032:analysis* / Q000235:genetics; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D005779:Immunodiffusion; D007122:Immunoelectrophoresis; D012487:Salmonidae / Q000276:immunology*; D014337:Trout / Q000276:immunology*; D014357:Trypsin / Q000378:metabolism
D000596:Amino Acids; D001798:Blood Proteins; D003176:Complement C3; D014357:Trypsin