Molecular cloning of equine preprorelaxin cDNA

A cDNA clone encoding preprorelaxin was isolated from the equine placental cDNA library and its nucleotide sequence was determined. Analysis of the sequence revealed that the cDNA contained a polyadenylation site and an open reading frame encoding 182 amino acids, including a signal peptide of 25 amino acids, a B-chain of 28, a C-peptide of 109 and an A-chain of 20 amino acids. The nucleotide sequence of preprorelaxin shows homology with those of the pig (75.5%), monkey (67.4%), human (67.4%), rat (60.7%) and mouse (54.6%). The main differences between equine preprorelaxin and that of these other species were the insertion of a Leu residue at position 87 in the C-peptide and also the deletion of two residues from the C-peptide and A-chain. Northern blot analysis of mRNA obtained from pregnancy day 70 placenta showed that there were two different sizes of mRNA (1.0 and 1.8 kb).