Molecular cloning and sequence analysis of the porcine precursor of endothelin-2

The amino acid sequences of two of the three endothelin (ET) family peptides, ET-1 and ET-3, are identical among mammals, whereas for the other family member, ET-2 or vasoactive intestinal contractor (VIC), the mouse and rat sequences differ from the human counterpart ET-2 by one amino acid residue. To examine more deeply the structural diversity among ET-2/VIC orthologs (EDN2), we screened porcine ET-2/VIC-like cDNAs using the 5' rapid amplification of cDNA ends (RACE) method with degenerate primers based on ET-2/VIC mature peptides. Sequence analysis of the cDNAs showed that ET-2 is present in pig. The full-length cDNA sequence, produced by combining 5' RACE and 3' RACE products, revealed the porcine precursor protein of ET-2 (PPET-2). Porcine PPET-2, made up of 214 amino acids, includes a 26-residue putative signal sequence, big ET-2, mature ET-2, and ET-2-like peptide. The percent sequence identity of porcine PPET-2 with human PPET-2, and rat or mouse precursor protein of VIC runs between approximately 70% and 74%. ET-2, although expressed in intestine, has no anti-microbial activity.