Soluble factors stimulating secretory protein translocation in bacteria and yeast can substitute for each other

mRNA for prepro-alpha-factor (pp alpha), a yeast secretory glycoprotein, was translated in a wheat germ cell-free system that was posttranslationally supplemented either with inverted vesicles from the plasma membrane of Escherichia coli (INV) or with microsomes from Saccharomyces cerevisiae. A postribosomal supernatant (PRS) from E. coli was found to stimulate translocation of pp alpha across the INV membrane. A yeast PRS could substitute for its E. coli counterpart. Likewise, an E. coli PRS could substitute for a yeast PRS and stimulate translocation of pp alpha across yeast microsomal membranes.