Fig. 4.

Protease protection assays. S. cerevisiae MM476 cells were transformed with the indicated plasmids (see Fig. 1), and purified vacuoles were treated with proteinase K in the presence or absence of Triton X-100. Western blot was probed with anti-HA antibodies as described in Materials and Methods. Relative molecular masses are indicated (Left). The molecular masses of different polypeptides (indicated by arrowheads) are discussed in the text. Results are representative of at least three independent experiments.