Chemical Modification of the Membrane-bound ATP Synthetase of Spinach Chloroplasts with Pyridoxal Phosphate in Light

概要

論文の詳細を見る
Photosynthetic activities of the thylakoid membranes modified with pyridoxal phosphate (PLP) and sodium borohydride in light were studied and compared with those modified in the dark. PLP modified the membrane-bound chloroplast coupling factor l (CF_1) and inhibited photophosphorylation. Only PLP modification in light stimulated basal electron transport. This stimulation of electron transport was prevented by the presence of ATP or carbonylcyanide m-chlorophenylhydrazone in the modification mixture. Magnesium ion was required for PLP modification. The extent of light-induced proton uptake was decreased by PLP modification in light. N,N'-Dicyclohexyl-carbodiimide lowered the stimulated electron transport to the basal level of unmodified chloroplasts and restored proton uptake. When chloroplasts were modified with 4 mM PLP in light and dark, 11.6 and 11.0 mol of PLP were incorporated into mol of CF_1, respectively. ATP could bind with high affinity to CF_1 isolated after PLP modification in light. The results indicate that PLP modifies membrane-bound CF_1 which has a conformation altered by energization of the thylakoids in light, and causes an apparent uncoupling of phosphorylation (stimulation of basal electron transport). The results suggest that this uncoupling is induced by the loss of the regulatory function of CF_1 for proton translocation after PLP modification in light.
日本植物生理学会の論文