We previously reported that the reductive activities of yeast protein disulfide isomerase (yPDI) family proteins did not completely explain their contribution to the viability of Saccharomyces cerevisiae [Kimura et al. (2004) Biochem Biophys Res Commun. 320, 359-365]. In this study, we examined oxidative refolding activities and found that Mpd1p,Mpd2 and Eug1p exhibit activities of 13.8 %,16.0 % and 2.16 %, respectively, compared to Pdi1p, and that activity for Eps1p is undetectable. In analyses of interactions between yPDI proteins and endoplasmic reticulum (ER) molecular chaperones, we found that Mpd1p alone does not have chaperone activity but that it interacts with and inhibits the chaperone activity of Cne1p, a homologue of mammalian calnexin, and that Cne1p increases the reductive activity of Mpd1p. These results suggest that the interface between Mpd1p and Cne1p is near the peptide binding site of Cne1p. In addition, Eps1p interacts with Pdi1p, Eug1p, Mpd1p and Kar2p with dissociation constants (KD) in the range of 10-7 ~ 10-6 M. Interestingly, co-chaperone activities were completely suppressed in Eps1p-Pdi1p and Eps1p-Mpd1p complexes, although Eps1p and Pdi1p alone have chaperone activity. The in vivo consequences of these results are discussed.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|