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

Work with DPAP B, a type II vacuolar membrane protein homologous to DPAP A, has shown that no domain of the protein contains positive targeting information for the vacuole (Roberts et al., 1992) . The targeting signal for a second vacuolar membrane protein, alkaline phosphatase, has not been identified although the lumenal domain is not required for the correct localization of this protein (Klionsky and Emr, 1990) . The authors concluded that the vacuolar-sorting determinant must therefore reside in the cytoplasmic and/or membrane-spanning domain of alkaline phosphatase, but in light of the data presented here and elsewhere (Roberts et al., 1992) , these results could be reinterpreted to suggest that the membrane association of alkaline phosphatase mediates its vacuolar delivery.