The primary substrate binding site in the b' domain of ERp57 is adapted for endoplasmic reticulum lectin association

摘要: ERp57 is a member of the protein disulfide isomerase (PDI) family that located in endoplasmic reticulum (ER) and characterized by its specificity for glycoproteins. Substrate selection dependent upon formation discrete complexes with two ER resident lectins, soluble calreticulin membrane-bound calnexin. It these lectins directly associate glycoproteins bearing correctly trimmed oligosaccharide side chains. Thus, presented preselected set substrates which it can act, specific binding calnexin to pivotal functions resulting complexes. To gain further insights into ERp57-ER lectin complexes, we have investigated regions are specifically required calreticulin. Using quantitative pull-down assay investigate ERp57/PDI chimeras calreticulin, define b b′ domains as minimal elements sufficient complex formation. This analysis identifies novel role distinctive C-terminal extension reconstituting wild type levels. our understanding substrate domain PDI paradigm, show alterations residues dramatically reduce or completely abolish On basis data, propose model where region equivalent primary site archetypal occupied suggest act adaptor molecules ERp57.