Folding in vitro of bovine pancreatic trypsin inhibitor in the presence of proteins of the endoplasmic reticulum

Abstract

The rate of folding and disulfide bond formation in reduced BPTI were measured in vitro in the presence and absence of total protein from the endoplasmic reticulum. The rates were increased substantially by the endoplasmic reticulum proteins, but only to the extent expected from the known content and activity of protein–disulfide–isomerase. No effects of added ATP or Ca²⁺ were observed, even though protein–disulfide–isomerase blinds Ca²⁺ tightly.