PDI family protein ERp29 forms 1:1 complex with lectin chaperone calreticulin

Lectin chaperone calreticulin is well known to interact with ERp57 which is one of PDI family proteins. The interaction of ERp57 with calreticulin is believed to assist disulfide bond formation of nascent glycoprotein in the ER. Various kinds of PDI family proteins are present in the ER, however, their precise roles have been unclear. In this study, interaction assay between PDI family proteins and calreticulin by SPR analysis was performed. Our analysis revealed for the first time formation of a 1:1 complex between ERp29 and calreticulin. The dissociation constant of interaction between ERp29 and calreticulin was shown to be almost identical to ERp57-calreticulin interaction. We speculate that the recognition site of ERp29 within calreticulin is different from that of ERp57.