FIG. 2.

Effect of weak bases on the accumulation of methylammonium (A) and glucose (B) by S. cerevisiae (see Materials and Methods). Transport by strain 23344c (wild type) was assessed after exposure to buffer at pH 7.5 (squares) or to buffer containing 1 mM chloroquine (2 μM unprotonated form; triangles) or 200 mM NH₄Cl (3.5 mM NH₃; circles). (A) The initial concentration of [¹⁴C]methylammonium was 6 μM. Cells were grown in minimal medium with proline (10 mM) as the N source. (B) The initial concentration of d-[1-¹⁴C]glucose was 170 μM. Cells were grown in modified YPD containing 0.05% glucose.