Overexpression and Functional Stabilization of Recombinant Human Lysophosphatidic Acid Receptor 1 Using an Amphiphatic Polymer

Human lysophosphatidic acid receptor 1 (LPA1 ) is a G‐protein coupled receptor that mediates various biological functions such as proliferation, platelet aggregation, smooth muscle contraction, and tumor cell invasion. For dissection of the molecular function of LPA1 , a recombinant LPA1 was overexpressed in Escherichia coli membrane fractions and purified to homogeneity by single affinity chromatography. The purified LPA1 was stabilized with an amphiphilic polymer that was synthesized by the coupling of octylamine, glucosamine, and diethylaminoproylamine at the carboxylic groups of poly‐γ‐glutamic acid. The complex of purified LPA1 and amphiphilic polymer showed a monodisperse oligomer and specific binding to LPA with apparent Ki values of 30 μM. Compared with the Gs protein, it also showed selective binding to the alpha subunit of the Gi protein. These results indicate that recombinant LPA1 in an amphiphilic polymer complex has an active conformation for interaction with ligands and G‐proteins.