Chromaffin granule H⁺-ATPase has F₁-like structure

Isolated H⁺-ATPase from chromaffin granules was reconstituted into liposomes and the resultant proteoliposomes were further purified by Ficoll density gradient centrifugation. Studies by electron microscopy showed that proteoliposomes had particle structures (average diameter, about 10 nm) on their outer surface. These particles could be removed from the proteoliposomes by cold treatment. Immuno-electron microscopy showed that these particles were recognized by antibodies against the hydrophilic sector of the enzyme. These results indicate that the H⁺-ATPase has a peripheral membrane structure similar to that of F₁-ATPase.