Fig. 3.

Preparation of a buoyant cholesterol-rich endomembrane membrane fraction. Equal volumes of all subcellular fractions were subjected to SDS-PAGE separation and immunoblotted for (A) the mitochondrial marker protein prohibitin (1:2000), the ER protein calnexin (1:5000), and the plasma membrane-associated protein syntaxin-4.(1:1000). (B) Distribution of cholesterol as measured using the Amplex red cholesterol assay. Data are presented as percentage of total cholesterol measured across the gradient. Antibody dilutions used are in parentheses. ER, endoplasmic reticulum.