Homodimerization of neurotensin 1 receptor involves helices 1, 2, and 4: insights from quaternary structure predictions and dimerization free energy estimations

A computational approach based upon rigid-body docking, ad hoc filtering, and cluster analysis has been combined with a protocol for dimerization free energy estimations to predict likely interfaces in the neurotensin 1 receptor (NTS1) homodimers. The results of this study suggest that the likely intermonomer interfaces compatible with in vitro binding affinity constants essentially involve helices 1, 2, and 4 and do not include disulfide bridges. The correlative model initially developed on Glycophorin A and herein extended to a G protein-Coupled Receptor (GPCR) appears to be a useful tool for estimating the association free energies of transmembrane proteins independent of the size and shape of the interface. In the desirable future cases, in which in vitro intermonomer binding affinities will be available for other GPCRs, such a correlative model will work as an additional criterion for helping in the selection of the most likely dimers.