Protein disulfide isomerase (PDI) is a component of the microsomal triglyceride transfer protein (MTP) complex. This study was initiated to help elucidate the role of PDI in MTP. The 88-kDa polypeptide of MTP (88K) was dissociated from PDI by using chaotropic agents (NaClO4 and KSCN), low concentrations of a denaturant (guanidine hydrochloride) or a nondenaturing detergent (octyl glucoside). As assessed by fluorescence and circular dichroism spectroscopy, these three different approaches appeared to dissociate the components of MTP under mild, nondenaturing conditions. The dissociating agents were diluted or removed by dialysis, and the free PDI and 88K were further characterized. In all cases, the dissociation coincided with the loss of triglyceride transfer activity. The free 88-kDa polypeptide readily aggregated, suggesting that it is a hydrophobic peptide. Even in the presence of chaotropic agents, when 88K was not aggregated, transfer activity was not expressed. These results suggest that the association of PDI with 88K is necessary to maintain the catalytically active form of the triglyceride transfer protein and prevent the aggregation of 88K.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.