Translation and processing of normal (PiMM) and abnormal (PiZZ) human α1‐antitrypsin

Abstract
Human liver mRNA isolated from subjects phenotyped as homozygous PiMM or PiZZ α1-antitrypsin, was translated in a reticulocyte cell-free system, and α1-antitrypsin identified by immunoprecipitation. In the presence of dog pancreas membranes the translated α1-antitrypsin appeared as a larger product. Treatment with endo-β-N-glucosaminidase yielded a protein smaller than the reticulocyte translated product, presumably due to removal of the N-terminal signal sequence by membranes and sugar residues by endo-β-N-glucosaminidase. Quantitation of α1-antitrypsin translated from PiMM and PiZZ livers suggests that both mRNA species were present at the same cellular concentration, and that processing to the core glycosylation stage proceeded at identical rates.