Post-nuclear membranes derived from yeast strains expressing Sss1pWT, Sss1pYG, or Sss1pF were solubilized in 1% Triton X-100 and Sec61 complexes were resolved by sucrose gradient centrifugation through a linear 0–15% sucrose gradient. Gradient samples were divided into 13 fractions, acid precipitated, and analyzed by SDS-PAGE and immunoblotting with antibodies to Sec61p, Sss1p, and Sbh1p. The positions of molecular weight standards run in parallel experiments are shown: Cytochrome c, 12 kDa; BSA, 67 kDa.