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Purification of Native Properdin by Reversed Affinity Chromatography and Its Activation by Proteolytic Enzymes¹

Department of Pathology, Division of Experimental Pathology, and Institute of Immunology, University of Toronto, Toronto, Canada

Abstract

A highly purified preparation of human properdin (P) has been obtained in a simple two-step procedure utilizing reversed application of the technique of affinity chromatography. The method involved precipitation of properdin from human serum and subsequent passage through an immunoadsorbent column of Sepharose anti-RP globulin which bound the contaminating proteins. The immunochemical properties of the isolated properdin (P) was found to be different from those of activated properdin (). P was shown to be a 6.1S, ₂ globulin with a mean subunit m.w. of 57,900. on the other hand was a 5.1S protein with ₂ mobility and a subunit m.w. of 53,000 daltons. Double diffusion analysis using anti- revealed a reaction of identity between P and . However, when the reaction was developed with anti-P, a reaction of partial identity was obtained and the precipitin line of P was seen to spur over the line developed with . Mild treatment with plasmin or trypsin converted P to .

Unlike , P was ineffective in triggering the activation of the Properdin System in RP unless trace amounts of zymosan were added. Under these conditions P was found to be converted to . The results indicate that properdin is present in fresh serum in a precursor form and its activation to involves a limited proteolytic cleavage of the molecule.

Footnotes

¹ This work was supported by the Ontario Heart Foundation, Banting Research Foundation and the Medical Research Council of Canada (MA-5063).

² Research Scholar of the Canadian Heart Foundation.