FIG. 3.

Manganese trafficking under manganese surplus or toxicity conditions. When S. cerevisiae cells are grown in the presence of surplus manganese (≈10 to 100 μM), the metal is taken up largely in the form of manganese-phosphate complexes via the Pho84p phosphate transporter. Two major manganese detoxification systems sequester the metal and help eliminate excess manganese from the cell. A bulk of the excess manganese is pumped into the Golgi via Pmr1p and the metal then exits the cell via the secretory pathway. Manganese is also delivered into the yeast vacuole by Ccc1p and perhaps by Cos16p as well. The action of vacuolar Mam3p is not known, but it helps contribute to manganese toxicity.