Purification of the fourth, second and fifth components of mouse complement

Area of Science:

• Immunology
• Biochemistry

Background:

• The complement system is crucial for innate and adaptive immunity.
• Functional characterization of individual mouse complement components is essential for understanding its complex roles.
• Previous studies lacked purified, active mouse complement components C4, C2, and C5.

Purpose of the Study:

• To purify functionally active mouse complement components C4, C2, and C5 from plasma.
• To characterize the molecular properties of purified C4, C2, and C5.
• To establish a reliable method for obtaining these key complement proteins.

Main Methods:

• Purification involved sequential polyethylene glycol precipitation, ion exchange chromatography, and gel filtration.
• Protein homogeneity was assessed using SDS-PAGE.
• Molecular weights of polypeptide chains were determined.

Main Results:

• Homogeneous preparations of C4, C2, and C5 were obtained with yields of 8.5%, 32%, and 40%, respectively.
• C4 comprised three chains (90,000, 78,000, 32,000 Da); C2 a single chain (115,000 Da) cleaved into 80,000 and 35,000 Da fragments by C1s.
• C5 consisted of two chains (135,000 and 84,000 Da). The C4b2a complex had a half-life of 7 minutes.

Conclusions:

• This is the first report detailing the successful purification of functionally active mouse complement components C4, C2, and C5 from plasma.
• The characterized molecular weights and subunit compositions provide critical data for the mouse complement system.
• These purified components enable further investigation into complement-mediated biological processes.