Abstract
After preliminary characterization of C3 converting factor (C3 CoF) the question was raised whether this factor was a “true” activator of C3, i.e. generates C3a and C3b on interaction with native C3. For this purpose C3 NeF and C3 CoF activity were separated from each other by euglobulin precipitation and anion exchange chromatography using a discontinuous salt gradient. The C3 CoF containing fraction was devoid IgG. To identify the site of cleavage in the C3 molecule C3 was isolated from normal human serum to apparent homogeneity and radiolabelled with 125-iodine using the Bolten-Hunter method. Incubation of this radiolabelled C3 with C3 CoF isolated from patient's serum generated two major C3 fragments identified by autoradiography following SDS-PAGE under reducing conditions: A large fragment with 117 kD and a small fragment with approx. 10 kD. Following autoradiography proteins were transblotted on nitrocellulose and analyzed for expression of C3 antigens using the Western blot technique and monospecific antisera to C3a and C3c. The 117 kD fragment expressed C3c antigen but no C3a antigen, the 10 kD fragment expressed C3a antigen only indicating that C3 was, indeed, cleaved into C3a and C3b. We conclude that C3 CoF is a “true” activator of C3.
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Wahn, V., Schwertz, R., Buhl, R. et al. BIOCHEMICAL ACTION OF C3 CONVERTING FACTOR (C3 COF) ON THE THIRD COMPONENT OF HUMAN COMPLEMENT. Pediatr Res 19, 1073 (1985). https://doi.org/10.1203/00006450-198510000-00032
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DOI: https://doi.org/10.1203/00006450-198510000-00032