A cryoelectron microscopy study of the interaction of the Escherichia coli F1-ATPase with subunit b dimer.

A complex between the Escherichia coli F1-ATPase and a truncated form of the ECF0-b subunit was formed and examined by cryoelectron microscopy in amorphous ice. Image analysis of single particles in the hexagonal projection revealed that the polar domain of the b subunit interacts with a beta subunit different from the one which interacts with the epsilon subunit. The cavity in the enzyme, visible in the hexagonal projection, is not filled by the b polypeptide, therefore leaving enough room for extensive conformational changes of the gamma and epsilon subunits within the native F1F0 complex.