Expression and pharmacological characterization of the human μ‐opioid receptor in the methylotrophic yeast Pichia pastoris

Abstract

The human μ‐opioid receptor cDNA from which the 32 amino‐terminal codons were substituted by the Saccharomyces cerevisiae α‐mating factor signal sequence has been expressed in the methylotrophic yeast Pichia pastoris using the host promoter of the alcohol oxidase‐1 gene. Cell membranes exhibited specific and saturable binding of the opioid antagonist [³H]diprenorphine (K _d = 0.2 nM and B _max = 400 fmol/mg protein or 800 sites/cell). Competition studies with non‐selective, and μ‐, δ‐ and κ‐selective opioid agonists and antagonists revealed a typical μ‐opioid receptor binding profile, suggesting proper folding of the protein in yeast membranes.