The chloroplast ATP synthetase consist of the subunits α, β, γ, δ, ϵ and proteolipid only Evidence that the components termed subunit I and II are proteolytically altered light-harvesting proteins

AbstractThe subunit stoichiometry of the ATP synthetase (CF1-CF0) immunoprecipitated from Triton X-100 extracts of chloroplast thylakoid membranes was determined to be α3, β3, γ, δ, ϵ (CF1) and I0.3, II0.6–0.9, III4(6) (CF0). Antibodies against the polypeptides α, β, γ, δ, I, II and ϵ combined specifically with the isolated subunits as analysed by the protein blotting method. Applying this technique, antibodies against the CF1 subunits were found to form complexes with the corresponding polypeptides of thylakoids, whereas those against I (Mr 20 000) and II (Mr 17 000) combined with Mr 26 000 and Mr 24 500 membrane polypeptides, respectively. The Mr 26 000 polypeptide was identified as the major subunits of the light-harvesting chlorophyll a/b-protein (LHCP) complex and the Mr 24 500 component seems to be functionally connected with this complex. From the results it is concluded that the chloroplast ATP synthetase consists of the subunit of the α, β, γ, δ, ϵ and III (proteolipid only and that proteolytically altered LHCP polypeptides bind artifically to the protein complex during isolation