[Quaternary structure of thyroglobulin (author's transl)]

Porcine and ovine thyroglobulins were purified from fresh glands by slice extraciton, precipitation with buffered ammonium sulfate and Sepharose 6B gel filtration using 0.1 M sodium phosphate buffer pH 7.2 at all steps. In contrast to thyroglobulin obtained from frozen glands, the proteins purified from unfrozen glands only showed the 19 S and 12 S species by electrophoresis in sodium dodecylsulfate polyacrylamide gels. After full reduction and S-alkylation, no qualitative changes were observed in e gel electrophoresis patterns as compared to the unmodified proteins. Species of apparent molecular weight corresponding to the native 12 S subunit was the major component strongly suggesting a mol. wt. of about 330 000 for the elementary peptide chains of pig and sheep thyroglobulin. This was confirmed by sedimentation equilibrium analyses in 6 M guanidinium. HCl, 0.1 M sodium phosphate pH 7.2 OF FULLY REDUCED AND S-alkylated thyroglobulins which showed a weight average molecular weight of 310 000 daltons.