PMID:11694508

Citation	Winter, J, Klappa, P, Freedman, RB, Lilie, H and Rudolph, R (2002) Catalytic activity and chaperone function of human protein-disulfide isomerase are required for the efficient refolding of proinsulin. J. Biol. Chem. 277:310-7
Abstract	Protein-disulfide isomerase (PDI) catalyzes the formation, rearrangement, and breakage of disulfide bonds and is capable of binding peptides and unfolded proteins in a chaperone-like manner. In this study we examined which of these functions are required to facilitate efficient refolding of denatured and reduced proinsulin. In our model system, PDI and also a PDI mutant having only one active site increased the rate of oxidative folding when present in catalytic amounts. PDI variants that are completely devoid of isomerase activity are not able to accelerate proinsulin folding, but can increase the yield of refolding, indicating that they act as a chaperone. Maximum refolding yields, however, are only achieved with wild-type PDI. Using genistein, an inhibitor for the peptide-binding site, the ability of PDI to prevent aggregation of folding proinsulin was significantly suppressed. The present results suggest that PDI is acting both as an isomerase and as a chaperone during folding and disulfide bond formation of proinsulin.
Links	PubMed Online version:10.1074/jbc.M107832200
Keywords	Catalysis; Genistein/pharmacology; Humans; Molecular Chaperones/physiology; Proinsulin/chemistry; Protein Disulfide-Isomerases/antagonists & inhibitors; Protein Disulfide-Isomerases/physiology; Protein Folding
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
HUMAN:PDIA1		GO:0006457: protein folding	ECO:0000314:		P		Figure 1 shows increased refolding of proinsulin in cells with PDI in comparison to those lacking PDI.	complete CACAO 4892

References

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