Characterization of a cDNA for human glutathione-insulin transhydrogenase (protein-disulfide isomerase/oxidoreductase)

Electron microscopic visualization of fluorescent signals in cellular compartments and organelles by means of DAB-photoconversion

In this work, we show the photoconversion of the fluorochromes enhanced green fluorescent protein (EGFP), yellow fluorescent protein (YFP), and BODIPY into electron dense diaminobenzidine (DAB)-deposits using the examples of five different target proteins, and the lipid ceramide. High spatial resolution and specificity in the localization of the converted protein-fluorochrome complexes and the fluorochrome-labelled lipid were achieved by methodical adaptations around the DAB-photooxidation step, such as fixation, illumination, controlled DAB-precipitation, and osmium postfixation. The DAB-deposits at the plasma membrane and membranous compartments, such as endoplasmic reticulum and Golgi apparatus in combination with the fine structural preservation and high membrane contrast enabled differential topographical analyses, and allowed three-dimensional reconstructions of complex cellular architectures, such as trans-Golgi-ER junctions. On semithin sections the quality, distribution and patterns of the signals were evaluated; defined areas of interest were used for electron microscopic analyses and correlative microscopy of consecutive ultrathin sections. The results obtained with the proteins golgin 84 (G-84), protein disulfide isomerase (PDI), scavenger receptor classB type1 (SR-BI), and gamma-aminobutyric acid (GABA) transporter 1 (GAT1), on one hand closely matched with earlier immunocytochemical data and, on the other hand, led to new information about their subcellular localizations as exemplified by a completely novel sight on the subcellular distribution and kinetics of the SR-BI, and provided a major base for the forthcoming research.

Nucleotide sequence of the porcine 60S ribosomal protein L35 cDNA

The cDNA encoding the 60S ribosomal protein L35 was cloned from the porcine liver cDNA library using the N-terminal fragment coding region of human protein disulfide isomerase as the probe.

Two isoforms of protein disulfide isomerase alter the dimerization status of E2A proteins by a redox mechanism

We have shown previously that E2A helix-loop-helix proteins spontaneously form an intermolecular disulfide cross-link that is required for stable homodimer binding to DNA (Benezra, R. (1994) Cell 79, 1057-1067). These homodimers are important for the development of B lymphocytes but are not present in other cell lineages. We have purified two proteins that are capable of regulating the formation of this disulfide bond and found them to be members of the protein disulfide isomerase (PDI) family. By regulating the formation of the disulfide cross-link, these proteins are capable of regulating the dimerization state of E proteins. PDI-mediated reduction appears to dissociate E protein homodimers and favors heterodimer formation with other basic helix-loop-helix proteins in both a purified protein system and in cellular extracts. These studies suggest that PDI may play an important role in the regulation of E2A transcription factor dimerization and the development of the B lymphocyte lineage.

Cloning of a cDNA encoding an Acanthamoeba castellanii PDI-like protein

We have cloned, from Acanthamoeba castellanii, the cDNA encoding a new member of the protein disulfide isomerase (PDI)-like protein family. The new PDI-like protein contains two highly conserved thioredeoxin-like domains, each about 100 amino acids in length. However, the A. castellanii PDI-like protein differs from other members in many aspects, including the overall organization and isoelectric point. Southern and Northern analyses demonstrate that the PDI-like protein is encoded by a single-copy gene which is transcribed to generate a 1500-nucleotide mRNA.

Expression and purification of recombinant rat protein disulfide isomerase from Escherichia coli

Rat liver protein disulfide isomerase (PDI) catalyzes the oxidative folding of proteins containing disulfide bonds. We have developed an efficient method for its overproduction in Escherichia coli. Using a T7 RNA polymerase expression system, isolated yields of 15-30 mg/liter of recombinant rat PDI are readily obtained. Convenient purification of the enzyme from E. coli lysates involves ion-exchange (DEAE) chromatography combined with zinc chelate chromatography. The recombinant PDI shows catalytic activity identical to that of PDI isolated from bovine liver in both the reduction of insulin and the oxidative folding of ribonuclease A. The enzyme is expressed in E. coli as a soluble, cytoplasmic protein. After complete reduction and denaturation in 6 M guanidinium hydrochloride, PDI regains complete activity within 3 min after removal of the denaturant, implying that disulfide bonds are not essential for the maintenance of PDI tertiary structure. Both the protein isolated from E. coli and the protein isolated from liver contained free cysteine residues (1.8 +/- 0.2 and 1.4 +/- 0.3 SH/monomer, respectively).

Protein disulphide isomerase from human peripheral blood neutrophils

Protein disulphide isomerase (PDI) is a 56 kDa resident polypeptide of the endoplasmic reticulum of many cell types. We evaluated the ability of human peripheral blood polymorphonuclear neutrophils (PMN) to synthesize both mRNA and proteins. Using in vitro [35S]-methionine labeling of purified PMN, followed by immunoprecipitation of cell lysates with immobilized polyclonal and monoclonal antibodies and analysis by gel electrophoresis, PMN were shown to synthesize many proteins, including actin. In contrast, incorporation of [35S]-methionine into PDI was not detected. Purification of total RNA from PMN and analysis by Northern blots demonstrated the presence in PMN of PDI-RNA. Western immunoblot evaluations of total PMN protein display an immunoreactive-PDI of 56 kDa. Indirect immunofluorescence studies suggest an abundance of immunoreactive-PDI throughout PMN. We therefore conclude that PDI is synthesized in precursor cells of the bone marrow. Phorbol 12-myristate 13-acetate, a reagent known to affect the degranulation of specific granules, causes the release of immunoreactive-PDI into a post-centrifugation supernatant. PDI, a ubiquitous endoplasmic reticulum resident protein, is shown here to be associated with specific granules in a cell type which has lost its intracellular membrane network during terminal differentiation.