Partial deglycosylation of chloroplast coupling factor 1 (CF1) prevents the reconstitution of photophosphorylation.

Treatment of spinach chloroplast coupling factor 1 (CF1) with a mixture of glycosidases resulted in the removal of approximately 75% of the carbohydrate associated with the enzyme. The ATPase of CF1 was not activated by this treatment nor were its heat-activated or methanol-dependent ATPase activities inhibited. The deglycosylated enzyme, however, was unable to catalyze photophosphorylation when recoupled with CF1-depleted thylakoids. The glycosidase-treated protein competed with native CF1 for specific binding sites on the depleted membranes and was able to reconstitute proton uptake in uncoupled thylakoids. The inhibition of photophosphorylation could not be overcome with added delta subunit. We conclude that deglycosylated CF1 was unaffected in its ability to bind to the membrane sector of the chloroplast proton-pumping ATPase (CF0) but was altered in some property essential for photophosphorylation but not ATPase activity.