INFLUENCE OF THE CLATHRIN COAT ON THE MEMBRANE LIPIDIC ORGANIZATION OF ENDOCYTIC VESICLES - A FLUORESCENCE STUDY

Endocytic coated vesicles (CV) were purified from bovine brain, and un coated vesicles (UV) were obtained from the latter by dialysis against 1 M Tris. Membrane dynamics were explored in both vesicle populations using two complementary fluorescence approaches: diphenylhexatriene f luorescence anisotropy to account for rotational lipid movements, and pyrene excimerization with a phosphatidylcholine pyrene derivative for translational motion. It was concluded that membrane fluidity was con siderably higher in UV than in CV, and that adding bulk coat proteins (adaptors + clathrin) to uncoated vesicles re-established the low flui dity found in coated vesicles. However, adding coat protein constituen ts separately had no effect.