Electron microscopic evidence of two stalks linking the F1 and F0 parts of the Escherichia coli ATP synthase

The structure of monodisperse ATP synthase from Escherichia coli (ECF1F0) has been examined by electron microscopy after negative staining of specimens. The F-1 part is seen to be connected by two stalks. One is more centrally located and includes the gamma and epsilon subunits. The second stalk, observed here in ECF1F0, is arranged peripherally. It probably contains the delta and b subunits which, in addition to gamma and epsilon, are required for binding of the F-1 and F-0 parts of the complex. Other novel features of the F1F0 complex can be discerned. There is a cap at the top of the F-1 part at which the second stalk may bind. This likely includes N-terminal stretches of the three copies of the a subunit and a part of the delta subunit. The F-1 part is clearly asymmetric. The presence of two stalks in the complex has important functional implications. There is good evidence that the more central stalk of gamma and epsilon subunits is a mobile domain that rotates to link the three catalytic sites on beta subunits in turn, with the proton channel of the F-0 part. The second stalk of delta and b subunits is then the stator which makes this rotation possible. (C) 1998 Elsevier Science B.V.