Purification and Partial Characterization of the third Component of the Complement System from Porcine Serum (C3) and of a Crystallizable Degradation Product of the fourth Component of the Complement System from Human Serum (C4). Study of the Tryptic Digestion Products of Human and Porcine C3 and of Human C4

Abstract

The 3rd component of the porcine complement system (C3) was isolated. The protein with 190,000 MW was composed of 2 chains, .alpha. and .beta., of MW 116,000 and 74,000. The amino acid composition is very similar to that of human C3. A degradation product of human C4 was also isolated and characterized. This protein was crystallized. The degradation product was characterized by a MW of 128,000; the major part of the .alpha.-chain was lost. Native human and porcine C3 and human C4 were submitted to tryptic digestion. The digestion products were isolated and characterized in terms of MW, subunit organization and amino acid composition. The high homology among these proteins was confirmed.