Identification of protein disulphide-isomerase as a major acidic polypeptide in rat liver microsomal membranes

Abstract

Protein disulfide-isomerase was purified to homogeneity from rat liver by a rapid high-yielding procedure. Structural properties of the pure enzyme were very similar to those of the bovine liver enzyme purified by the same method. The purified rat liver enzyme was subjected to 2-dimensional gel electrophoresis in the presence and in the absence of microsomal membranes, and shown to co-electrophorese with a major acidic polypeptide cleary identifiable in the 2-dimensional electrophoretic profile of microsomal membranes. This identification was confirmed by peptide mapping of the pure enzyme and of the defined spot from a 2-dimensional electrophoresis gel.