Recombinant expression, in vitro refolding, and biophysical characterization of the N-terminal domain of T1R3 taste receptor

► We overexpress the human N-terminal domain of T1R3 (hT1R3-NTD) as inclusion bodies using Escherichia coli. ► Using a fractional factorial screen, we found conditions for the refolding of hT1R3-NTD. ► Biophysical approaches showed that hT1R3-NTD is functional. ► This strategy is a prerequisite for structural determination of NTD of other class C GPCRs.