DNAJB9
Domain
The J domain stimulates the ATPase activity of HSPA5/BiP, while the divergent targeting domain is required for efficient substrate recognition by HSPA5/BiP. The divergent targeting domain specifically recognizes and binds to aggregation-prone sequences.
Function
Co-chaperone for Hsp70 protein HSPA5/BiP that acts as a key repressor of the ERN1/IRE1-mediated unfolded protein response (UPR) (By similarity). J domain-containing co-chaperones stimulate the ATPase activity of Hsp70 proteins and are required for efficient substrate recognition by Hsp70 proteins (PubMed:18400946). In the unstressed endoplasmic reticulum, interacts with the luminal region of ERN1/IRE1 and selectively recruits HSPA5/BiP: HSPA5/BiP disrupts the dimerization of the active ERN1/IRE1 luminal region, thereby inactivating ERN1/IRE1 (By similarity). Also involved in endoplasmic reticulum-associated degradation (ERAD) of misfolded proteins. Required for survival of B-cell progenitors and normal antibody production (By similarity).
Tissue Specificity
Widely expressed. Expressed at highest level in the liver, placenta and kidney (PubMed:11836248).
Cellular localization
- Endoplasmic reticulum lumen
Alternative names
MDG1, UNQ743/PRO1471, DNAJB9, DnaJ homolog subfamily B member 9, Endoplasmic reticulum DNA J domain-containing protein 4, Microvascular endothelial differentiation gene 1 protein, ER-resident protein ERdj4, ERdj4, Mdg-1