Functional coupling with Gα q and Gα i1 protein subunits promotes high-affinity agonist binding to the neurotensin receptor NTS-1 expressed in Escherichia coli

Abstract

To analyze the coupling of Gα subunits to the rat neurotensin receptor NTS-1 (NTR), fusion proteins were expressed in Escherichia coli with various Gα subunits covalently linked to the receptor C-terminus. The presence of Gα q or Gα i/q, in which the six C-terminal residues of Gα i1 were replaced with those from Gα q, increased the percentage of receptors in the agonist high-affinity state. This effect was less pronounced for wild-type Gα i1 and not observed for Gα i/s. Functional coupling of neurotensin receptor to Gα was demonstrated by neurotensin-induced [ 35S]GTPγS binding for the Gα q, Gα i/q and Gα i1 subunits, but not for Gα i/s. Our results extend previous findings of the dual coupling of NTR to pertussis toxin-sensitive and -insensitive G-proteins in Chinese hamster ovary cells with preference for the latter.