Cloning and Expression in Escherichia coli of Full-Length Complementary DNA Coding for Human α ₁ -Antitrypsin

A cDNA library prepared from human liver was screened for alpha 1-antitrypsin, a major constituent of plasma which functions as inhibitor of proteolytic enzymes. The library was screened using a 12-base-long synthetic oligodeoxyribonucleotide corresponding to a known DNA fragment of human alpha 1-antitrypsin and by hybrid-selection of alpha 1-antitrypsin mRNA. A plasmid, pULB1523, was identified carrying a cDNA insert of about 1400 bp coding for human alpha 1-antitrypsin. Restriction mapping and DNA sequence analysis indicated that the 1400 bp code for the signal peptide and for the complete mature alpha 1-antitrypsin molecule. In addition, a solid-phase enzyme-linked immunoassay showed that pULB1523 expresses human alpha 1-antitrypsin in bacteria. Fusion of the alpha 1-antitrypsin sequence to the leader sequence of the beta-lactamase gene (plasmid pKT287) resulted also in the expression of the protein in bacteria.