Direct visualisation of conformational changes in EF(0)F(1) by electron microscopy.

The isolated H(+)-ATPase from Escherichia coli (EF(0)F(1)) was investigated by electron microscopy of samples of negatively stained monodisperse molecules, followed by single-particle image processing. The resulting three-dimensional maps showed that the F(1)-part is connected by a prominent stalk to a more peripheral part of F(0). The F(1)-part showed stain-accessible cavities inside. In three-dimensional maps from selected particles, a second stalk could be detected which was thinner than the main stalk and is thought to correspond to the stator.Three-dimensional maps of the enzyme in the absence and in the presence of the substrate analogue adenyl-beta, gamma-imidodiphosphate (AMP-PNP) were calculated. Upon binding of AMP-PNP the three-dimensional maps showed no significant changes in the F(0)-part of EF(0)F(1), whereas a major conformational change in the F(1)-part was observed. (1) The diameter of the F(1)-part decreased upon binding of AMP-PNP mainly in the upper half of F(1). (2) Enzyme particles prepared in the presence of AMP-PNP had a pointed cap at the top of the F(1)-part which was missing in its absence. (3) The stain-accessible cavity inside the F(1)-part altered its pattern significantly.