Human anaphylatoxin (C3a) from the third component of complement. Primary structure.

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Citation

Hugli TE

Human anaphylatoxin (C3a) from the third component of complement. Primary structure.

J Biol Chem. 1975 Nov 10;250(21):8293-301.

PubMed ID
1238393 [ View in PubMed
]
Abstract

C3a anaphylatoxin is derived from the third component (C3) of the blood complement system. Selective proteolysis of C3 by activated proenzymes indigenous to blood generates the C3a fragment. Human C3a was isolated from inulin-activated serum containing 6-aminohexanoic acid, according to recently published procedures (Hugli, T. E., Vallota, E., and Muller-Eberhard, H. J. (1975) J. Biol. Chem. 250, 1472-1498). The human C3a fragment is a highly cationic molecule exhibiting an approximate molecular weight of 9000 and composed of 77 amino acid residues. It consists of a single polypeptide chain containing 8% cysteine and lacks both tryptophan and carbohydrate. A tentative primary structure for the human C3a molecule, deduced from overlapping peptides obtained after cyanogen bromide cleavage, tryptic and chymotryptic digestion, is: See article. Two cystelhylcysteine sequences were established at positions 22, 23 and 56, 57 in human C3a. The 6 half-cystine residues in C3a are all interconnected through three disulfide linkages intersecting in a disulfide knot. The functionally amino acid residues distributed among 14 residues at the COOH-terminal end of C3a. This unusually cationic COOH-terminal region of C3a is presumed to play an important role in the interaction of this protein molecule with cellular receptors. A comparison between the linear sequence of human C3a and the NH2-terminal sequences of light and heavy chains of human immunoglobulin indicates that limited identity exists.

DrugBank Data that Cites this Article

Polypeptides
NameUniProt ID
Complement C3P01024Details