Targeting of aminopeptidase I to the yeast vacuole is mediated by Ssa1p, a cytosolic member of the 70-kDa stress protein family.
The two cytosolic members of the highly conserved 70-kDa stress protein family, Ssa1p and Ssa2p, were specifically retained by the prepro-NH(2) extension of the vacuolar aminopeptidase I precursor (pAPI) conjugated to agarose (Sulfolink). A temperature-sensitive mutant strain a1(ts)a234 (ssa1(ts) ssa2 ssa3 ssa4), when incubated at the restrictive temperature, was able to assemble the API precursor into dodecamers, but failed to pack pAPI into vesicles and to convert it into mature API (mAPI), a process that occurs in the vacuole. Altogether these results indicate that Ssa1p mediates the targeting of pAPI to the vacuole.
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Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior Investigaciones Cientificas-Universidad Autónoma de Madrid, 28029 Madrid, Spain. isandoval@cbm.uam.es
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Gevaert
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Goethals
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Vandekerckhove
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Leber
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Sandoval
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D000251:Adenosine Triphosphatases; D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000378:metabolism*; D002846:Chromatography, Affinity; D003600:Cytosol / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins; D013696:Temperature; D014617:Vacuoles / Q000201:enzymology*
D018840:HSP70 Heat-Shock Proteins; D029701:Saccharomyces cerevisiae Proteins; D000626:Aminopeptidases; C019689:APE1 protein, S cerevisiae; D000251:Adenosine Triphosphatases; C095973:SSA1 protein, S cerevisiae