Amino acid sequence of guinea pig C3a anaphylatoxin

Abstract

The anaphylatoxin peptide, C3a, was isolated in its inactive des-arginine form from complement-activated guinea pig serum and the complete amino acid sequence was determined. The peptide was isolated using a modification of previously described methods for anaphylatoxin purification and yielded 18 mg of guinea C3ades Arg judged homogeneous by cellulose acetate electrophoresis, high performance liquid chromatography, amino acid composition, and sequence analyses. The complete amino acid sequence of the molecule was determined by automated Edman degradation of intact C3ades Arg following performic acid oxidation, and of four peptides obtained from CNBr, endoproteinase Lys-C, or endoproteinase Glu-C (V8 protease) digests of reduced and alkylated C3ades Arg. The sequence is as follows: Guinea pig C3ades Arg has approximately 70% overall sequence identity with human, porcine, rat and mouse anaphylatoxins. As with C3a's from other species, the guinea pig molecule has an invariant C-terminal tetrapeptide sequence, LGLA, and six invariant cysteinyl residues at positions 23, 24, 37, 50, 57, and 58.