Classical complement pathway components C1r and C1s: purification from human serum and in recombinant form and...

Area of Science:

• Biochemistry
• Immunology
• Proteomics

Background:

• The classical complement pathway is initiated by the C1 complex, comprising C1q, C1r, and C1s.
• C1r and C1s are serine proteases essential for complement activation and effector functions.
• The C1 complex circulates as an inactive zymogen, activated by target recognition, typically via C1q binding to immune complexes.

Purpose of the Study:

• To describe methods for purifying active and zymogen forms of C1r and C1s proteases.
• To detail the purification of the proenzyme C1s-C1r-C1r-C1s tetramer.
• To present biochemical and functional characterization techniques for these complement proteins and their complex.

Main Methods:

• Purification of C1r and C1s from human serum utilizing immune complex binding and EDTA-mediated dissociation.
• Separation of C1r and C1s via ion-exchange chromatography and reassembly of the tetramer using calcium ions.
• Isolation of the reconstituted tetramer by gel filtration and production of recombinant C1s and tetramer in a baculovirus-insect cell system followed by affinity chromatography.

Main Results:

• Successful purification of both activated and proenzyme forms of C1r and C1s from human serum.
• Isolation and characterization of the proenzyme C1s-C1r-C1r-C1s tetramer.
• Demonstration of recombinant C1s and tetramer production and purification.

Conclusions:

• Established protocols for the purification and characterization of key classical complement pathway proteases.
• Provided methods for obtaining functional C1r, C1s, and their tetrameric complex for further research.
• Enabled the study of complement activation mechanisms through purified and recombinant proteins.