PMID: 2579379

 

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Title : Human complement component C3: cDNA coding sequence and derived primary structure

Abstract :
  1. The complete cDNA coding sequence and derived amino acid sequence of human complement component C3 are presented
  2. The encoded precursor molecule contains a signal peptide of 22 amino acid residues , the beta chain (645 residues ), and the alpha chain (992 residues )
  3. The two chains are joined by four arginine residues not present in the mature protein
  4. Several functionally important sites have been localized, such as the thiolester site , the cleavage site liberating the anaphylatoxin, and two sites of cleavage by the serine protease factor I , as well as a peptide fragment with leukocyte mobilizing activity
  5. At least two carbohydrate attachment sites , one on each chain, have been identified
  6. Human C3 has 79% identity to mouse C3 at the nucleotide level and 77% identity at the amino acid level
  7. The protease alpha 2-macroglobulin and complement component C4 show considerable homology to C3, suggesting that the three proteins have evolved from a common ancestor