Replacement of domain b of human protein disulfide isomerase‐related protein with domain b^′ of human protein disulfide isomerase dramatically increases its chaperone activity

Abstract

We have reported that human protein disulfide isomerase-related protein (hPDIR) has isomerase and chaperone activities that are lower than those of the human protein disulfide isomerase (hPDI), and that the b domain of hPDIR is critical for its chaperone activity [J. Biol. Chem. 279 (2004) 4604]. To investigate the basis of the differences between hPDI and hPDIR, and to determine the functions of each hPDIR domain in detail, we constructed several hPDIR domain mutants. Interestingly, when the b domain of hPDIR was replaced with the b' domain of hPDI, a dramatic increase in chaperone activity that was close to that of hPDI itself was observed. However, this mutant showed decreased oxidative refolding of alpha1-antitrypsin. The replacement of the b domain of hPDIR with the c domain of hPDI also increased its chaperone activity. These observations suggest that putative peptide-binding sites of hPDI determine both its chaperone activity and its substrate specificity.

Structure of the Non-Catalytic Domain of the Protein Disulfide Isomerase-Related Protein (PDIR) Reveals Function in Protein Binding

“…Of these domains, the second catalytic domain (CGHC) exhibited the highest isomerase activity on model substrates, while the CSMC domain was most important for the folding of α 1 -antitrypsin [7]. Interestingly, replacement of the non-catalytic domain of PDIR with the substrate-binding b 'domain of PDIA1 increases the chaperone activity of PDIR to PDIA1 levels, but decreases oxidative refolding of α 1 -antitrypsin [9]. This suggests that in a fashion analogous to other PDI proteins, the non-catalytic domain of PDIR plays a key role in binding substrates and chaperone partners.…”

Functional Relationship between Protein Disulfide Isomerase Family Members during the Oxidative Folding of Human Secretory Proteins

“…The structure of yeast PDI reveals a U-shaped orientation of its four thioredoxin-like domains, termed a , b , b′ , and a′ , where a and a′ denote the catalytically active domains containing the CXXC motif and b and b′ are noncatalytic domains (Kemmink et al , 1997; Tian et al , 2006). The b′ domain appears to be the main site for substrate binding and for the reported chaperone functions of PDI (Klappa et al , 1998; Horibe et al , 2004). There is a hydrophobic surface within the interior of the U structure that is provided by the b′ domain as well as the other domains that appears well suited for interaction with nonnative folding intermediates (Tian et al , 2006).…”

Unfolded protein response is not activated in the mucopolysaccharidoses but protein disulfide isomerase 5 is deregulated

“…Pdia5 (protein disulfide isomerase family A, member 5), also known as PDIr, first identified by Hayano and Kikuchi (1995), belongs to the family of protein disulfide isomerases (PDIs), enzymes that mediate oxidative protein folding in the ER by acting as dithiol-disulfide oxidoreductase to reduce, oxidize and isomerize disulfide bonds; these enzymes also show chaperone activity both in vitro and in vivo (Ellgaard and Ruddock 2005;Kozlov et al 2010). However, Pdia5 appears to be somewhat different from the other members of PDI family, in that it does not show significant peptide thiol-disulfide oxidase activity and its isomerase and chaperone activities are lower than those of the human PDIs (Horibe et al 2004a;Horibe et al 2004b;Alanen et al 2006). Therefore, the Pdia5 protein does not appear to be involved in the efficient catalysis of thiol-disulfide oxidation reactions; its functions are at the moment unclear, although it was suggested to play a critical role in the late complex-isomerization steps required for the generation of native disulfide bonds in nascent polypeptide chains (Alanen et al 2006).…”