The thermal denaturation of clathrin-coated vesicles isolated from bovine brain tissue has been studied by differential scanning calorimetry and has been compared to basket structures reformed from isolated triskelion trimers of clathrin and to isolated triskelions. The coated vesicles and reformed baskets displayed similar, yet distinct, thermal behavior. Calorimetric data of the coated vesicles exhibited a single denaturation transition peak at 55.9 ± 0.1 °C, skewed to low temperatures whereas the thermograms for the reformed baskets exhibited a broad transition peak at 53.1 ± 0.1 °C and a peak at 56.3 ± 0.1 °C. Neither transition was reversible. The specific transition enthalpy was 11.5 ± 1.0 J g-1 for the coated vesicles and the total transition enthalpy was 9.1 ± 0.3 J g-1 for the reformed baskets. In contrast, isolated triskelions showed no thermal transition between 15 and 90 °C. Although the coated vesicles and the reformed baskets have similar stability reflecting their similar structures, the coated vesicles appear to be marginally more stable than the reformed baskets. The complexity of the transition profiles and their lack of symmetry suggest the existence of several, somewhat independent, domains unique to the cage-like structure of the coated vesicles and reformed baskets.
Bibliographical noteFunding Information:
*Center for Chemical Technology, National Institute of Stam!ards and Technology, Gaithersburg, Ma&and 20899,a nd ~&&oratory of Biochemistry and Metabolism, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Marylund 208%’