Interactions of endothelin receptor subtypes A and B with Gi, Go, and Gq in reconstituted phospholipid vesicles

Biochemistry. 1999 Mar 9;38(10):3090-9. doi: 10.1021/bi981919m.


To understand the biochemical basis for the functional divergence of the human endothelin receptor subtypes A (ETAR) and B (ETBR), they were expressed, purified from insect Sf9 cells, and reconstituted into phospholipid vesicles with the Go, Gq, and Gi proteins. For each G protein, a unique pattern of reactivity was observed with the different receptor subtypes. Both ETAR and ETBR activated Go to a similar maximal extent, and both subtypes activated Gq with similar EC50 values; however, the ETAR displayed a 2-3-fold higher maximal extent of activation. In contrast, both subtypes activated Gi to a similar maximal extent, but the ETAR displayed a 4-fold higher EC50 value as compared to the ETBR. To test whether these coupling specificities are influenced by C-terminal palmitoylation of the receptor, we mutated a cluster of cysteine residues near the end of the seventh transmembrane helix in both receptors. While the cysteine mutations in the ETBR resulted in a partially palmitoylated receptor, the replacement of these cysteine residues in the ETAR yielded a mostly palmitoyl-deficient receptor and had no effect on Go activation, but caused a reduction in the extents of Gi and Gq stimulation. Together, these studies provide important insights into the specificity of G protein coupling in the endothelin receptors. The ability to discriminate between the different G proteins under various physiological conditions may be a key element in the selection of distinct signal transduction pathways by the two receptor subtypes.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cattle
  • Epitopes / genetics
  • GTP-Binding Protein alpha Subunits, Gi-Go / metabolism*
  • GTP-Binding Proteins / metabolism*
  • Gene Transfer Techniques
  • Histidine / genetics
  • Humans
  • Ligands
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Palmitic Acid / metabolism
  • Phospholipids / metabolism*
  • Protein Structure, Secondary
  • Rats
  • Receptor, Endothelin A
  • Receptor, Endothelin B
  • Receptors, Endothelin / genetics
  • Receptors, Endothelin / isolation & purification
  • Receptors, Endothelin / metabolism*
  • Spodoptera / genetics


  • Epitopes
  • Ligands
  • Phospholipids
  • Receptor, Endothelin A
  • Receptor, Endothelin B
  • Receptors, Endothelin
  • Palmitic Acid
  • Histidine
  • GTP-Binding Proteins
  • GTP-Binding Protein alpha Subunits, Gi-Go