The stalk connecting the F1 and F0 domains of ATP synthase visualized by electron microscopy of unstained specimens

E. coli F1F0 ATP synthase has been reconstituted into membranes and visualized by electron microscopy of unstained samples preserved in thin layers of amorphous ice. Unlike previous observations in negative stain, these specimens are not exposed to potentially denaturing or perturbing conditions, having been rapidly frozen from well-defined conditions in which the enzyme is fully active. The structures visualized in views normal to the lipid bilayer clearly show the presence of a narrow stalk approx. 45 A long, connecting the F1 to the membrane-embedded F0.