FIG. 2. Distribution of proteins along the sucrose gradient. Sperm were extracted with 0.5% Triton X-100 and subjected to ultracentrifugation on a sucrose gradient as described in Materials and Methods. Nine fractions were collected from top to bottom and were analyzed by SDS-PAGE and Western blot using different antibodies. The molecular weights of the bands shown are in the right column. In the case of SPAM1 and ADCY10, bands shown are those marked with an arrowhead in Figure 1 . A nonraft protein (ADCY10) was included as control.