Splitting of human thyroglobulin. I. Reduction and alkylation.

Human thyroglobulin was purified by ammonium sulphate precipitation followed by DEAE column chromatography. It produced a single line in double diffusion precipitation reactions in gel and immunoelectrophoresis, and was devoid of serum-related antigens. The preparation was reduced by 2-mercaptoethanol and alkylated by iodoacetamide in the presence and the absence of 8 M-urea. In the absence of urea, the reduced, alkylated product was still capable of inhibiting the tanned cell haemagglutinin reaction of human autoantiserum or rabbit heteroantiserum with native thyroglobulin. The rabbit, but not the human, antiserum precipitated reduced, alkylated thyroglobulin in agar gel. By immunoelectrophoresis, three antigens migrating faster than thyroglobulin were seen with the rabbit antiserum. The same preparation, reduced and alkylated in the presence of 8 M-urea, failed to react with either the rabbit or human antisera.