FIG. 4.

Peptide and ATP affect the self-association of Cer1p. (A) The top panel is the Western blot analysis of the fractions from a 10 to 35% sucrose gradient loaded with crude microsomal extract from a CER1-overexpressing strain. Fraction 1 represents the top of the gradient, while P is the pellet fraction. In the lower panel, ATP was added to a final concentration of 1 mM in the gradient and in the extract and then immediately loaded onto the gradient at 4°C. (B) The same gradients and analysis were used to determine the effect of peptide SO81, which was absent in the top gradient and present in the bottom gradient. In both gradients the extract was incubated at 22°C with or without peptide for 20 min before it was loaded on the column.