Two resident ER‐proteins, CaBP1 and CaBP2, with thioredoxin domains, are substrates for thioredoxin reductase: comparison with protein disulfide isomerase

FEBS Letters

Rupp, Katrin¹  Birnbach, Ulrike¹  Lundström-Ljung, Johanna²  Söling, Hans-Dieter¹  Holmgren, Arne² 

[1] Abteilung Klinische Biochemie, Zentrum Innere Medizin, Universität Göttingen, Postfach 3742, D-3400 Göttingen, Germany;Medical Nobel Institute for Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institute, S-171 77 Stockholm, Sweden

关键词: Protein disulfide-isomerase;    Thioredoxin;    Thioredoxin reductase;    Protein folding;    Endoplasmic reticulum;    Redox potential;    PDI;    protein disulfide-isomerase;    CaBP1;    calcium binding protein 1 from rat liver microsomes;    CaBP2;    calcium binding protein 2 from rat liver microsomes;    DTT;    dithiothreitol;    DTNB;    5;    5′-dithiobis(2-nitrobenzoic acid);    Trx;    E. coli thioredoxin;    P34H Trx;    E. coli thioredoxin with Pro-34 mutated to His;    TR;    thioredoxin reductase;    E′0;    redox potential;   

DOI  :  10.1016/0014-5793(94)01386-F

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Protein disulfide-isomerase (PDI) is the best known representative of a growing family of enzymes with thioredoxin domains. Two such proteins with thioredoxin (Trx) domains, CaBP1 and CaBP2 (ERp72), have previously been isolated from rat liver microsomes. Here we report that they, like PDI are substrates for thioredoxin reductase and will catalyze NADPH-dependent insulin disulfide reduction. The activity of CaBP1 and CaBP2 in this assay was higher than that of PDI but lower than that of E. coli Trx. Furthermore, as isolated the thioredoxin domains of CaBP1 and CaBP2 were in disulfide form as judged by stoichiometric oxidation of 2 and 3 mol of NADPH in CaBP1 and CaBP2, respectively. The redox potential of the active site disulfide/dithiol was estimated from the equilibrium with a mutant E. coli Trx, P34H Trx, with a known redox potential (−235 mV). This showed that CaBP1 and CaBP2, like PDI, have a much higher redox potential than wild type thioredoxin (−270 mV) in agreement with a role in formation of protein disulfide bonds. In conclusion, in vitro CaBP1 and CaBP2 share catalytic properties in thiol disulfide-interchange reactions with PDI. Thus, the well known activity of PDI is not unique in the endoplasmic reticulum and CaBP1 and CaBP2 may be regarded as functional equivalents.

【 授权许可】

Unknown