Localization of the δ subunit in the Escherichia coli F1F0-ATPsynthase by immune electron microscopy:: The subunit δ binds on top of the F1

The binding site of the delta subunit in the F1F0-ATPsynthase from Escherichia coli has been determined by electron microscopy of negatively stained, antibody-decorated enzyme molecules. The images show that the antibody is bound at the very top of the F-1 domain indicating that at least part of delta is bound in the dimple formed by the N termini of the alpha and beta subunits. The data may explain why there is only one binding site for delta ore the F-1 despite there being three identical alpha beta pairs. The finding also implies that the b subunits of the F-0 have to extend all the way from the membrane surface to the very top of the F-1 domain to make contact with the delta subunit. (C) 2000 Academic Press.