PROTON GRADIENT-INDUCED CHANGES OF THE INTERACTION BETWEEN CF0 AND CF1 AS PROBED BY CLEAVAGE WITH NASCN

Treatment of isolated thylakoids from spinach chloroplasts with the ch aotropic salt NaSCN results in release of CF1 together with a variety of other proteins. The detachment of the CF1 polypeptides by 0.5 M NaS CN was much higher in illuminated than in non-illuminated samples. The CF1 subunits are released at about the same molar ratio as in the ent ire complex, suggesting that NaSCN cleaves primarily between CF0 and C F1. However, subsequent dissociation of CF1 into smaller aggregates or individual subunits may occur. Detachment of CF1 from pea thylakoids requires somewhat higher NaSCN concentrations, but a distinct light/da rk difference is nevertheless found. The enhancement of CF1 solubiliza tion by light is largely abolished by the uncoupler nigericin, suggest ing that the proton gradient affects the interaction between CF0 and C F1. The enhanced release is also reduced by the CF0 blocker DCCD, indi cating that the translocation of protons through CF0 is necessary. The enhancement is partially abolished by the substrates of phosphorylati on, ADP and phosphate, suggesting that the change of interaction betwe en the subcomplexes is connected with the process of energy transducti on in CF0CF1.