Characterization of a novel porcine endothelinB receptor splice variant

Screening of porcine cerebellum cDNA library with porcine endothelin(B) (ETB) receptor cDNA revealed a novel ETB receptor cDNA that is distinctly different from the wild-type ETB receptor in length and the amino acid sequence at the C-terminal end. This sequence appears to represent alternate splicing of the carboxy terminal end of ETB receptor, resulting in a polypeptide of 429 amino acids in length, which is 14 amino acids shorter than the wild-type porcine ETB receptor. Characterization of the wild-type and alternately spliced ETB receptors expressed in COS cells revealed that both receptors displayed very similar binding [apparent dissociation constant (K-d) and maximum binding (B-max) for I-125-ET-1 were 71 pM and 1.6 pmol/mg protein for wild-type and 81 pM and 1.2 pmol/mg protein for splice variant ETB receptors] as well as functional properties. These data suggest that the differences in the amino acids at the C-terminal end had no effect on binding or functional coupling of these alternately spliced ETB receptors.