Isolation of component C4 of human complement and its polypeptide chains

Area of Science:

• Biochemistry
• Immunology
• Protein Chemistry

Background:

• The human complement system is crucial for innate and adaptive immunity.
• Component C4 (C4) plays a central role in complement activation pathways.
• Understanding C4 structure and properties is essential for immunological research.

Purpose of the Study:

• To develop an efficient purification method for human complement component C4.
• To characterize the molecular weight and subunit composition of purified C4.
• To determine the amino acid composition of C4 and its constituent polypeptide chains.

Main Methods:

• Purification of C4 from fresh frozen plasma using quaternary aminoethyl-Sephadex batch separation.
• Column chromatography on DEAE-cellulose and gel filtration with Sephadex G-200 for purification.
• Polyacrylamide gel electrophoresis, immunochemical methods, sedimentation-equilibrium analysis, and gel filtration in guanidine hydrochloride for characterization.

Main Results:

• Achieved a 25% yield of homogenous human complement C4.
• Determined the molecular weight of C4 to be 189,000.
• Identified and determined the molecular weights of the alpha (88,000), beta (72,000), and gamma (32,000) polypeptide chains of C4.

Conclusions:

• A robust method for purifying human complement C4 was established.
• The molecular weight and subunit structure of human C4 were elucidated.
• This work provides foundational data on C4 composition for further immunological studies.