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Distribution of protein disulphide isomerase in rat liver mitochondria.

ABSTRACT: Here we report the localization of protein disulphide isomerase (PDI) in the mitochondrial compartments, comparing it with that of thioredoxin reductase. The latter enzyme is present mostly in the matrix, whereas PDI is located at the level of the outer membrane. We characterize the different submitochondrial fractions with specific marker enzymes. PDI, whether isolated from whole mitochondria or from purified outer membranes, exhibits the same electrophoretic mobility, indicating identical molecular masses. Moreover, immunoblot analysis with monoclonal anti-PDI antibody shows immunoreactivity only with the microsomal PDI, indicating the specificity of the mitochondrial isoform. The significance of these findings is discussed with reference to the potential role of PDI and thioredoxin reductase in regulating the mitochondrial functions dependent on the thiol-disulphide transition.

SUBMITTER: Rigobello MP

PROVIDER: S-EPMC1221870 | biostudies-other | 2001 Jun

REPOSITORIES: biostudies-other

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The latency of rat liver microsomal protein disulphide-isomerase.

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Transcriptional regulation of rat liver protein disulphide-isomerase gene by insulin and in diabetes.

Project description:The mRNA encoding for rat protein disulphide-isomerase (PDI) increases 3-fold in the liver of diabetic rats and is accompanied by similar changes at the protein level. Long treatment (for 3 days) of diabetic rats with insulin reverses this effect of diabetes both at the mRNA and protein levels. The higher expression of rat PDI mRNA in diabetes is due to an increase in the transcriptional rate of the gene, and insulin treatment of diabetic animals produces within 30 min a decrease in the level of transcription of PDI gene, as judged by nuclear run-on transcription experiments performed in vivo. These results clearly show a role for insulin in the regulation of transcription of the gene encoding this multifunctional protein in rat liver.

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Regulation of nerve growth and patterning by cell surface protein disulphide isomerase.

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

Project description:Protein disulphide-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 two-dimensional gel electrophoresis in the presence and in the absence of microsomal membranes, and shown to co-electrophorese with a major acidic polypeptide clearly identifiable in the two-dimensional electrophoretic profile of microsomal membranes. This identification was confirmed by peptide 'mapping' of the pure enzyme and of the defined spot from a two-dimensional electrophoresis gel.

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Thiol-protein disulphide oxidoreductases. Differences between protein disulphide-isomerase and glutathione-insulin transhydrogenase activities in ox liver.

Project description:1. Protein disulphide-isomerase and glutathione-insulin transhydrogenase activities were assayed in parallel through a conventional purification of protein disulphide-isomerase from ox liver. 2. Throughout a series of purification steps (differential centrifugation, acetone extraction, (NH4)2SO4 precipitation and ion-exchange chromatography), the two activities appeared in the same fractions but were purified to different extents. 3. The final sample was 143-fold purified in protein disulphide-isomerase but only 10-fold purified in glutathione-insulin transhydrogenase; nevertheless the two activities in this preparation were not resolved by high-resolution isoelectric focusing and both showed pI4.65. 4. In a partially purified preparation containing both activities, glutathione-insulin transhydrogenase was far more sensitive to heat denaturation than was protein disulphide-isomerase; conversely protein disulphide-isomerase was more sensitive to inactivation by deoxycholate. 5. The data are inconsistent with a single enzyme being responsible for all the protein disulphide-isomerase and glutathione-insulin transhydrogenase activity of ox liver. It is suggested that several similiar thiol-protein disulphide oxidoreductases of overlapping specificities may better account for the data.

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