Studies on the glycoprotein nature of the thyrotropin receptor: interaction with lectins and purification of the bovine protein with the use of Bandeiraea (Griffonia) simplicifolia I affinity chromatography.

The TSH receptor from Triton-solubilized bovine microsomal membranes was found to bind to a substantial extent to columns of the immobilized lectins Bandeiraea (Griffonia) simplicifolia I, Ricinus communis I, wheat germ, and Concanavalin A, whereas it was not retained by Dolichos biflorus. Elution of TSH receptor activity from these lectins could be achieved with the appropriate saccharides in all cases except Concanavalin A. The most extensive adsorption of the receptor occurred on B. simplicifolia I-agarose (84%), and the terminal alpha-D-galactosyl specificity of this interaction was substantiated by its susceptibility to alpha-galactosidase treatment. Whereas TSH itself was not bound to this immobilized lectin, a complex of this hormone with its receptor did interact and could be eluted with methyl-alpha-D-galactoside. Purification (800-fold) of the bovine TSH receptor was achieved by a combination of TSH and B. simplicifolia I affinity chromatographies. Polyacrylamide gel electrophoresis of the purified TSH receptor after radioiodination revealed three major components with apparent mol wt of 316,000, 115,000, and 54,000.