The isolation of a clone for human alpha 1-antitrypsin and the detection of alpha 1-antitrypsin in mRNA from liver and leukocytes

A recombinant clone containing an insert complementary to alpha 1-antitrypsin (alpha 1-AT) mRNA has been isolated from a human adult liver cDNA library. The clone was selected by direct screening of recombinants with a synthetic oligodeoxynucleotide 17 bases in length corresponding to the known partial DNA sequence of the gene. The insert size of the clone is 250 base pairs. The DNA sequence of the clone has been determined and agrees with the published partial DNA sequence. There is one nucleotide difference from the published sequence, causing a single amino acid change at position 376 where aspartate replaces glutamate. The clone has been used to detect alpha 1-AT mRNA sequences in human liver and in a mixed leukocyte population containing monocytes and lymphocytes. A single mRNA approximately 1,400 nucleotides in length is observed in both leukocytes and liver. Leukocytes contain only 0.15% as much alpha 1-AT mRNA as liver.