Modelling TSH and its Receptor Complex for Binding Affinity

Abstract

Thyroid stimulating hormone (TSH), a glycoprotein hormone consisting of two distinct subunits, binds to its receptor (TSHR) and regulates the production and secretion of thyroid hormones via a complex signaling cascade. Two recent works have reported the crystal structure of stimulating and blocking type antibody-Fab fragments binding to the ectodomain of the TSHR. However, as of today no crystal structure of the TSH-TSHR complex has been reported.In this work, homology modeling of TSH has been carried out with Modeller (Sali and Blundell 1993) using the crystal structure (PDB ID: 1FL7) of the related follicle stimulating hormone (FSH) as the template (Fox, Dias et al. 2001). A fast molecular dynamics minimization of the structure has been performed as part of the Modeller routine. Docking of TSH on the TSHR was carried out on the HEX server (http://hexserver.loria.fr/) and residual contacts of the TSH-TSHR complex have been identified. Conformational studies and the free energy of binding will be reported based on Molecular Dynamics simulations using the AMBER force field. The calculations will be complemented by experimental determination of the binding affinity using Surface Plasmon Resonance (SPR). This study provides useful insight into the kinetics and dynamics of TSH binding to its receptor.Fox, K. M., J. A. Dias, et al. (2001). Molecular Endocrinology 15(3): 378-389.Sali, A. and T. L. Blundell (1993). Journal of Molecular Biology 234(3): 779-815