Preparation of membrane-depleted polygonal coat structures from isolated coated vesicles

When coated vesicles isolated from porcine brain are treated with buffers containing 2 M urea and subjected to ultracentrifugation, pellets are obtained which consist of largely smooth-surfaced, i.e. coat-free, vesicles. On dialysis of the urea from the supernatant solution spheroidal particles can be pelleted which are of similar size to the coated vesicles and show the typical polygonal lattice arrays but do not reveal any vesicle membrane profiles. Gel electrophoresis of these membrane-depleted polygonal arrangements demonstrates the predominance, if not exclusive occurrence, of the polypeptide band component with an apparent molecular weight of about 180,000. This suggests that the polygonal coat structure contains only clathrin.