RETENTION OF A CO-TRANSLATIONAL TRANSLOCATED MUTANT PROTEIN OF CARBOXYPEPTIDASE-Y OF SACCHAROMYCES-CEREVISIAE IN ENDOPLASMIC-RETICULUM

Co-translational translocation of Saccharomyces cerevisiae vacuolar gl ycoprotein carboxypeptidase Y (CpY) was highly efficient when studied with an in vivo and in vitro homologous system, comparison of limited proteolytic cleavage of immunoprecipitated translational products of C pY and subcellular localisation of a mutant CpY. The efficient segrega tion of CpY mRNA in highly purified fractions of rough microsomes was characterised. CpY1 mutant showed retention Of CoTe glycosylated mater ial (proCpY1) in the rough and smooth endoplasmic reticulum fractions. It is suggested that the presence of structures that are incompatible with intercompartmental transport of vacuolar protein leads to retent ion of the mutated CpY by the endoplasmic reticulum.