Interactions among yeast protein-disulfide isomerase proteins and endoplasmic reticulum chaperone proteins influence their activities.
We previously reported that the reductive activities of yeast protein-disulfide isomerase (PDI) family proteins did not completely explain their contribution to the viability of Saccharomyces cerevisiae (Kimura, T., Hosoda, Y., Kitamura, Y., Nakamura, H., Horibe, T., and Kikuchi, M. (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 with Pdi1p and that activity for Eps1p is undetectable. In analyses of interactions between yeast PDI proteins and endoplasmic reticulum 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) to 10(-6). Interestingly, co-chaperone activities were completely suppressed in Eps1p-Pdi1p and Eps1p-Mpd1p complexes, although only Eps1p and Pdi1p have chaperone activity. The in vivo consequences of these results are discussed.
Department of Bioscience & Technology, Faculty of Science & Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga, 525-8577, Japan.
Taiji
T
Kimura
Yasuhiro
Y
Hosoda
Yoshimi
Y
Sato
Yukiko
Y
Kitamura
Takezo
T
Ikeda
Tomohisa
T
Horibe
Masakazu
M
Kikuchi
D037281:Calnexin; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology; D018832:Molecular Chaperones / Q000378:metabolism* / Q000502:physiology; D010084:Oxidation-Reduction; D019704:Protein Disulfide-Isomerases / Q000378:metabolism* / Q000502:physiology; D017510:Protein Folding; D025941:Protein Interaction Mapping; D012097:Repressor Proteins / Q000378:metabolism / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000502:physiology*
C080582:CNE1 protein, S cerevisiae; C402288:Eps1 protein, S cerevisiae; D006023:Glycoproteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; C080576:PDI1 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D037281:Calnexin; C095229:MPD1 protein, S cerevisiae; C076879:EUG1 protein, S cerevisiae; D019704:Protein Disulfide-Isomerases