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Updated: Apr 28, 2026

Split-Ubiquitin Based Membrane Yeast Two-Hybrid MYTH System: A Powerful Tool For Identifying Protein-Protein Interactions
Published on: February 2, 2010
Loss of BiP/GRP78 function blocks translocation of secretory proteins in yeast
J P Vogel1, L M Misra, M D Rose
1Department of Biology, Lewis Thomas Laboratory, Princeton University, New Jersey 08544-1014.
Abstract:
BiP/GRP78 is an essential member of the HSP70 family that resides in the lumen of the endoplasmic reticulum. In yeast, BiP/GRP78 is encoded by the KAR2 gene. A temperature sensitive mutation was isolated in KAR2 and found to cause a rapid block in protein secretion. Secretory precursors of a number of proteins (invertase, carboxypeptidase Y, alpha-factor, and BiP) accumulated that were characteristic of a block in translocation into the lumen of the ER. Protease protection experiments confirmed that the precursors accumulated on the cytoplasmic side of the ER membrane. Moreover, depletion of wild-type KAR2 protein also resulted in a block in translocation of secretory proteins. These results implicate BiP/GRP78 function in the continued translocation of proteins into the lumen of the ER.
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