CLONING AND CHARACTERIZATION OF THE BOVINE PLASMINOGEN CDNA

A bovine liver cDNA library was screened with oligonucleotide probes based on a partial bovine plasminogen cDNA sequence (Malinowski et al., 1984, Biochemistry, 23, 4243-50). Several cDNA clones were isolated and the nucleotide sequence revealed the amino acid sequence for plasminogen except for 21 N-terminal residues. The amino acid sequence of the N-terminal region and the pre-peptide was established after clotting and sequencing primer extension products. The cDNA has two possible start methionines, giving rise to pre-peptides of 26 and 19 amino acid residues, respectively, followed by, the nature plasminogen sequence of 786 amino acid residues. Three amino acid substitutions were found when the cDNA encoded protein was compared with the bovine protein sequence. Northern blotting analysis shelved that plasminogen is expressed in liver but not in mammary gland skeletal muscle mid heart. The lack of plasminogen expression in mammary gland was confirmed by tire screening of a bovine mammary gland cDNA, library with a bovine plasminogen cDNA probe, since no positive clones were detected.