Interaction of mature, unglycosylated and cell‐free synthesized rat α1‐proteinase inhibitor with elastase

Abstract

Purified rat .alpha.1-proteinase inhibitor (MW 54,000) and porcine pancreatic elastase (MW 26,000) formed a complex (MW 82,000) resistant to heat treatment under denaturing and reducing conditions. A similar .alpha.1-proteinase-inhibitor-elastase complex was detected by immunoprecipitation of .alpha.1-proteinase inhibitor from the medium of [35S]methionine-labeled hepatocyte primary cultures after incubation with elastase. Treatment of hepatocytes with tunicamycin led to the secretion of an unglycosylated .alpha.1-proteinase inhibitor (MW 41,000) which also formed a complex with elastase (MW 66,000). Complex formation (MW 68,000) could also be observed between cell-free synthesized pre-.alpha.1-proteinase inhibitor (MW 43,000) and elastase (MW 26,000). Evidently, neither glycosylation nor removal of the signal peptide are required for the formation of a biologically active conformation of .alpha.1-proteinase inhibitor.