Figure 6.

A thyroid-stimulating hormone receptor (TSHR)/Gs complex model. The nearly completed complex model between TSHR–TSH and Gs in an active conformation can be assembled based on information summarized in Figures 2 and 3. TSH (or thyrostimulin) binds at two sites in the TSHR, called binding site I (LRRD) and binding site II (hinge region), of which several specific amino acids mediate the contact and specificity for the hormone. This model provides structural information according to the general TSHR scheme in Figure 1, including the detailed disulfide bridges at the extracellular part, localization of the hinge region, or justification of the Gs molecule at the active TSHR structure conformation [based on the beta-2 adrenergic receptor/Gs complex PDB entry 3SN6 (118)].