Cytosolic Hsp70s are involved in the transport of aminopeptidase 1 from the cytoplasm into the vacuole

Eukaryotic 70 kDa heat shock proteins (Hsp70s) are localized in various cel lular compartments and exhibit functions such as protein translocation acro ss membranes, protein folding and assembly. Here we demonstrate that the co nstitutively expressed members of the yeast cytoplasmic Ssa subfamily, Ssa1 /2p, are involved in the transport of the vacuolar hydrolase aminopeptidase I from the cytoplasm into the vacuole, The Ssap family members displayed o verlapping functions in the transport of aminopeptidase 1, In SSAI and SSAI I deletion mutants the precursor of aminopeptidase I accumulated in a dodec americ complex that is packaged in prevacuolar transport vesicles, Ssa1/2p was prominently localized to the vacuolar membrane, consistent with the rol e we propose for Ssa proteins in the fusion of transport vesicles with the vacuolar membrane. (C) 2000 Federation of European Biochemical Societies.