The protected epitopes of TAb-8 and comparison of it to stimulating antibody epitopes.

<p><b>Panel A:</b> Though the epitopes of TAb-8 blocking TSHR-Ab looked similar to the stimulating antibodies there were, once again, some major differences in the residues contacted. Unlike the stimulators, the epitopes for this antibody in the LRD region were restricted to LRD 2, 3, 4 and 7 (red stars). The protected amino terminus segment was shorter and the hinge region segment was longer and extended to residue 291. <b>Panel B:</b> The comparison of blocking antibody (TAb-8) to that of stimulating antibodies MS-1 and M22 showed some unique regions (red stars) which may account for its ability to change the conformation of the receptor rendering it inert to TSH binding. The binding residues of stimulating TSHR antibody MS-1 are shown with blue stars and with purple stars. The purple stars indicate where both the blocker and the stimulator both protected residues.