Abstract
Summary
Because previous studies indicated that the nephritogenic antigen is sialoprotein, glomeruli were subjected to enzymic digestion and chromatographed to compare their sialic acid content and their ability to neutralize the anti-kidney antiserum.
The soluble fractions of glomerular trypsin digests contained all the sialic acid and the entire capacity to neutralize the anti-kidney serum. Sephadex G-200 chromatography was capable of separating the soluble digests into two high (A and B) and one low molecular weight compenent (C). They all contained sialic acid, but only the higher molecular weight fragments possessed the neutralizing capacity.
Pronase digests also contained most of the sialic acid, but these were completely inactive. Their chromatogram consisted almost entirely of the low molecular weight C peak, indicating that this less discriminating proteolytic enzyme completely degraded the protein portion of the antigen.
These findings seem to provide additional proof that the nephritogenic antigen is sialoprotein, but that degradation of the protein component leads to a loss of the neutralizing capacity.
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