Premium
Zinc metallation of yeast alkaline phosphatase and its protein level response to zinc
Author(s) -
Qiao Wei,
Ellis Charissa D.,
Wu Changyi,
Eide David J.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.611.16
Subject(s) - vacuole , zinc , chemistry , alkaline phosphatase , biochemistry , transporter , enzyme , serine protease , protease , cytoplasm , organic chemistry , gene
Alkaline phosphatase of Saccharomyces cerevisiae (ScALP/Pho8) is a zinc‐dependent vacuolar enzyme. ScALP moves through the secretory pathway as a zymogen before being activated by the Pep4 vacuolar protease. Interestingly, we found that both ScALP activity and protein level are affected by the availability of zinc ions; both decrease dramatically when cells are Zn limited and this effect is very specific to ScALP. Decreased ScALP level in low zinc was dependent on Pep4 suggesting that the apoprotein is degraded. By studying ScALP activity in wild type and various Zn transporter mutants, we found that ALP accumulation and activity is mainly dependent on the major vacuolar Zn transporters Zrc1 and Cot1, rather than zinc transporters acting upstream in the secretory pathway. Our experiments show that this transporter dependency is not due to direct channeling of zinc from these transporters to the enzyme nor is proteolytic activation in the vacuole required for metallation. Our current hypothesis is that the vacuolar environment is specifically favorable for ScALP metallation for two reasons. First, the level of zinc in the vacuole may be higher than in upstream compartments of the secretory pathway. Second, in vitro studies indicate that the low pH of the vacuole (5.5) promotes metal binding relative to more alkaline conditions. Failure to metallate ScALP in the vacuole results in its degradation by vacuolar proteases.