Isolation and Characterization of a Supramolecular Complex of Subunit III of the ATP-Synthase from Chloroplasts

Abstract

In SDS gels of purified, highly active ATP-synthase from chloroplasts, CF₀F₁ a protein band was detected at an apparent molecular weight of 100 kDa. This protein was isolated on a prepara­tive SDS gel. The 100 kDa protein can be dissociated at increased temperature or increased incubation time into an 8 kDa protein, which is identical with the subunit III of CF₀ (DCCD- binding protein or proteolipid). This implies that the 100 kDa band is a stable supramolccular complex containing at least 12 copies of subunit III. Electron micrographs reveal a diameter of 6.3 nm and a membrane spanning length of 6.1 nm. We assume that this supramolecular complex represents a stable native substructure of CF₀F₁.