VIP21 CAVEOLIN IS A CHOLESTEROL-BINDING PROTEIN/

MP21/caveolin is localized to both caveolae and apical transport vesic les and presumably cycles between the cell surface and the Golgi compl ex. We have studied the lipid interactions of this protein by reconsti tuting Escherichia coli-expressed VIP21/caveolin into liposomes. Surpr isingly, the protein reconstituted only with cholesterol-containing li pid mixtures. We demonstrated that the protein binds at least 1 mol of cholesterol per mole of protein and that this binding promotes format ion of protein oligomers. These findings suggest that VIP21/caveolin, through its cholesterol-binding properties, serves a specific function in microdomain formation during membrane trafficking.