Labelling and immunoprecipitation of thyroid microsomal antigen.

Human thyroid microsomes have been solubilized, labelled with 125I, immunoprecipitated with microsomal antibody and analysed by gel electrophoresis. The analysis indicated that two peptides of relative molecular masses 108 and 118 kDa, under reducing conditions, were specifically immunoprecipitated by microsomal antibody. Similar values were obtained under non-reducing conditions indicating that the two peptides were not linked by disulphide bridges to each other or to different peptides. These results suggest that the microsomal antigen contains two components which may be linked by non-covalent bonds to form a single protein of 230 kDa. Studies with lectin affinity columns suggested that the antigen was glycosylated.