Molecular properties of recombinant human alpha1-antitrypsin produced in Escherichia coli and in vitro translation system

Abstract

The cDNA encoding human al-antitrypsin (alAT) was expressed in Escherichia coli upto ？40% of total cellular proteins. The recombinant alAT carrying the Z type mutation (Glu342？>Lys) were accumulated as aggregates inside the E. coli cells while the wild type alAT were produced as a soluble form. The aggregation caused by the Z mutation became more significant as the growth temperature increased from 30 t to 37 t. A protein folding assay of alAT on SDS-polyaciylamide gel electrophoresis revealed that the Z polypeptides translated in vitro were in a conformation which could not bind elastase but rather served as a substrate for the protease. The results are consistent with the previously known Z type defects, aggregation inside the hepatocytes of patients and temperature-dependent oli-’ gomerization of the purified Z protein, ^rhe E. coli expression system and the folding (assay of in vitro translation product develoj)ed in the present study may be further explored / for characterization of other genetic variants of alAT.