THE PEPTIDE HDEF AS A NEW RETENTION SIGNAL IS NECESSARY AND SUFFICIENT TO DIRECT PROTEINS TO THE ENDOPLASMIC-RETICULUM

The key feature of tomato RNase LX localised solely outside the vacuol e is the C-terminal peptide HDEF which is very similar to known endopl asmic reticulum (ER) retention signals, For functional testing of the ER-targeting ability of HDEF, different constructs including the compl ete RNase LX, two truncated forms without HDEF and the truncated chiti nase FB7-1 Delta VTP C-terminally flanked by HDEF, were expressed in S accharomyces cerevisiae, The majority of RNase and chitinase, both con taining HDEF, accumulates within the ER, However, the truncated constr ucts without the peptide are released into the medium. We provide comp elling evidence that peptide HDEF at the C-terminus of secretory plant proteins is a new ER retention signal in yeast and most likely in pla nts, (C) 1998 Federation of European Biochemical Societies.