Yeast Kex1p is a Golgi-associated membrane protein: deletions in a cytoplasmic targeting domain result in mislocalization to the vacuolar membrane

An important implication of such default delivery is that yeast integral membrane proteins destined for the plasma membrane must have positive targeting information to either remain at the plasma membrane (proposal 3), or to avoid being diverted to the vacuole (proposal 4). It is pertinent that a mutation in the u-factor receptor (Ste3p), an integral plasma membrane protein, results in delivery of this protein to the vacuole, independent of the plasma membrane (Ho-recka, J., and G. Sprague, personal communication), raising the possibility that a plasma membrane targeting signal has been destroyed.