THYROID-STIMULATING PROPERTIES OF LONG-ACTING THYROID STIMULATOR GAMMAG-GLOBULIN SUBUNITS

Heavy and light chains were prepared from long-acting thyroid stimulator γG-globulin by reduction in 30 mM 2-mercaptoethanol followed by alkylation and chromatography on Sephadex G-75 in 1 M acetic acid. The time of exposure of the reduced and alkylated protein to acid was curtailed by collecting the column effluent in buffer. Heavy chain prepared under these conditions gave a short-acting response in the McKenzie bioassay. Light chain was inactive. Some reconstitution of γG-globulin occurred when the isolated chains were mixed in 1 M acetic acid and the short-acting response of the heavy chain was converted to a long-acting response similar to the original long-acting thyroid stimulator γG-globulin. The implication of these findings, in relation to the possible antibody nature of long-acting thyroid stimulator are discussed. © 1969.