FIRS Laboratories, RSR Ltd, Parc Ty Glas, Llanishen, Cardiff CF14 5DU, UK.
J Mol Endocrinol. 2012 Aug 30;49(2):137-51. doi: 10.1530/JME-12-0040. Print 2012 Oct.
Binding of a new thyroid-stimulating human monoclonal autoantibody (MAb) K1-18 to the TSH receptor (TSHR) leucine-rich domain (LRD) was predicted using charge-charge interaction mapping based on unique complementarities between the TSHR in interactions with the thyroid-stimulating human MAb M22 or the thyroid-blocking human MAb K1-70. The interactions of K1-18 with the TSHR LRD were compared with the interactions in the crystal structures of the M22-TSHR LRD and K1-70-TSHR LRD complexes. Furthermore, the predicted position of K1-18 on the TSHR was validated by the effects of TSHR mutations on the stimulating activity of K1-18. A similar approach was adopted for predicting binding of a mouse thyroid-blocking MAb RSR-B2 to the TSHR. K1-18 is predicted to bind to the TSHR LRD in a similar way as TSH and M22. The binding analysis suggests that K1-18 light chain (LC) mimics binding of the TSH-α chain and the heavy chain (HC) mimics binding of the TSH-β chain. By contrast, M22 HC mimics the interactions of TSH-α while M22 LC mimics TSH-β in interactions with the TSHR. The observed interactions in the M22-TSHR LRD and K1-70-TSHR LRD complexes (crystal structures) with TSH-TSHR LRD (comparative model) and K1-18-TSHR LRD (predictive binding) suggest that K1-18 and M22 interactions with the receptor may reflect interaction of thyroid-stimulating autoantibodies in general. Furthermore, K1-70 and RSR-B2 interactions with the TSHR LRD may reflect binding of TSHR-blocking autoantibodies in general. Interactions involving the C-terminal part of the TSHR LRD may be important for receptor activation by autoantibodies.
新的促甲状腺素人源单克隆自身抗体 (MAb) K1-18 与促甲状腺素受体 (TSHR) 亮氨酸丰富结构域 (LRD) 的结合通过基于 TSHR 与促甲状腺素人源 MAb M22 或甲状腺阻断人源 MAb K1-70 相互作用之间独特互补性的电荷-电荷相互作用映射进行预测。将 K1-18 与 TSHR LRD 的相互作用与 M22-TSHR LRD 和 K1-70-TSHR LRD 复合物的晶体结构中的相互作用进行比较。此外，通过 TSHR 突变对 K1-18 刺激活性的影响验证了 K1-18 在 TSHR 上的预测位置。采用类似的方法预测了鼠甲状腺阻断 MAb RSR-B2 与 TSHR 的结合。预测 K1-18 以与 TSH 和 M22 相似的方式结合到 TSHR LRD。结合分析表明，K1-18 轻链 (LC) 模拟 TSH-α 链的结合，而重链 (HC) 模拟 TSH-β 链的结合。相比之下，M22 HC 模拟 TSH-α与 TSHR 的相互作用，而 M22 LC 模拟 TSH-β与 TSHR 的相互作用。在 M22-TSHR LRD 和 K1-70-TSHR LRD 复合物（晶体结构）中观察到的与 TSH-TSHR LRD（比较模型）和 K1-18-TSHR LRD（预测结合）的相互作用表明，K1-18 和 M22 与受体的相互作用可能反映了一般的促甲状腺素自身抗体的相互作用。此外，K1-70 和 RSR-B2 与 TSHR LRD 的相互作用可能反映了一般的 TSHR 阻断自身抗体的结合。涉及 TSHR LRD C 端部分的相互作用对于自身抗体激活受体可能很重要。
