PMID: 2123190Nov 15, 1990Paper

Expression of acid phosphatase-beta-galactosidase hybrid proteins prevents translocation by depleting a soluble factor.

The Journal of Biological Chemistry
M R YoungP B Wolfe

Abstract

We have shown that hybrid proteins composed of the yeast repressible acid phosphatase (PHO5) and bacterial beta-galactosidase (lacZ) interfere with secretion of native acid phosphatase (Wolfe, P. B. (1988) J. Biol. Chem. 263, 6908-6915). We now report that PHO5-LacZ hybrid proteins have a more general effect on secretion and prevent translocation of several secreted proteins. Translocation of both the mating pheromone alpha-factor and the vacuolar protease carboxypeptidase Y is partially blocked when PHO5-LacZ hybrids are expressed. Cell fractionation and protease sensitivity indicate that alpha-factor and carboxypeptidase Y accumulate in precursor form on the cytoplasmic surface of the endoplasmic reticulum. Indirect immunofluorescence with antibody directed against beta-galactosidase supports the localization of hybrid proteins to the endoplasmic reticulum. Analysis of the hybrid protein phenotype in vivo and in vitro suggests that the hybrid proteins deplete a soluble factor required for efficient translocation across the endoplasmic reticulum. First, a decrease in the expression of a hybrid protein in vivo decreases its effect on translocation. Second, an in vitro translation/translocation reaction, prepared from a hybrid-b...Continue Reading

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