Characterization of the thyrotropin binding pocket

J Jeffreys, H Depraetere, J Sanders, Y Oda, M Evans… - Thyroid, 2002 - liebertpub.com
J Jeffreys, H Depraetere, J Sanders, Y Oda, M Evans, A Kiddie, T Richards, J Furmaniak…
Thyroid, 2002liebertpub.com
A panel of monoclonal antibodies (mAbs) to the thyrotropin receptor (TSHR) was prepared
using three different immunization strategies. The mAbs obtained (n= 138) reacted with
linear epitopes covering most of the TSHR extracellular domain and with conformational
epitopes. mAbs that bound to five different regions of the TSHR (amino acids [aa] 32-41, aa
36-42, aa 246-260, aa 277-296, and aa 381-385) were able to inhibit 125I-labeled
thyrotropin (TSH) binding to solubilized TSHR preparations. Fab and immunoglobulin G …
A panel of monoclonal antibodies (mAbs) to the thyrotropin receptor (TSHR) was prepared using three different immunization strategies. The mAbs obtained (n = 138) reacted with linear epitopes covering most of the TSHR extracellular domain and with conformational epitopes. mAbs that bound to five different regions of the TSHR (amino acids [aa] 32-41, aa 36-42, aa 246-260, aa 277-296, and aa 381-385) were able to inhibit 125I-labeled thyrotropin (TSH) binding to solubilized TSHR preparations. Fab and immunoglobulin G (IgG) preparations were similarly effective inhibitors for mAbs reactive with aa 246-260, aa 277-291 and aa 381-385 suggesting that these three regions of the TSHR are involved in TSH binding. In contrast mAbs reactive with aa 32-41 and aa 36-42 were not effective at inhibiting TSH binding when Fab preparations were used, suggesting that these N terminal regions of the TSHR were less critical for TSH binding. Our studies suggest that three distinct and discontinuous regions of the TSHR (aa 246-260 and 277-296 on the TSHR A subunit) and aa 381-385 (on the TSHR B subunit) fold together to form a complex TSH binding pocket. Alignment of the aa sequences of these three regions in TSHRs from different species indicates that they are highly conserved.
Mary Ann Liebert