FIG. 5.

Association of mutant and wild-type Ste18p proteins with internal and plasma membranes. Membranes from mutant and wild-type strains were fractionated on a Renografin gradient. Fractions were assayed for Ste4p (open circles), Ste18p (filled squares), and plasma membrane ATPase (dashed line) by immunoblotting methods. The ste18-C107S mutant protein was below the detectable level in the gradient fractions. (A) Strain W303-1A (STE18⁺). (B) Strain HC106S (ste18-C106S). (C) Strain HC107S (ste18-C107S).