The central plug in the reconstituted undecameric c cylinder of a bacterial ATP synthase consists of phospholipids.

The isolated rotor cylinder of the ATP synthase from Ilyobacter tartaricus was reconstituted into two-dimensional crystalline arrays. Atomic force microscopy imaging indicated a central cavity on one side of the rotor and a central plug protruding from the other side. Upon incubation with phospholipase C, the plug disappeared, but the appearance of the surrounding c subunit oligomer was not affected. This indicates that the plug consists of phospholipids. As the detergent-purified c cylinder is completely devoid of phospholipids, these are incorporated into the central hole from one side of the cylinder during the reconstitution procedure.