Traditionally, the canine pancreatic endoplasmic reticulum (ER) has been the workhorse for cell-free studies on protein transport into the mamma-lian ER. These studies have revealed multiple roles for the major ER-lumi-nal heat shock protein (Hsp) 70, IgG heavy chain-binding protein (BiP), at least one of which also involves the second ER-luminal Hsp70, glucose-reg-ulated protein (Grp) 170.