Studies on the System Regulating Proton Movement across the Chloroplast Envelope 1: Effects of ATPase Inhibitors, Mg

• Published in: Plant physiology (Bethesda) 1991-04, Vol.95 (4), p.1229-1236
• Main Authors: Peters, Jeanne S., Berkowitz, Gerald A.
• Format: Article
• Language: English
• Subjects: Metabolism and Enzymology
• ISSN: 0032-0889; 1532-2548

Studies were undertaken to further characterize the spinach ( Spinacea oleracea ) chloroplast envelope system, which facilitates H + movement into and out of the stroma, and, hence, modulates photosynthetic activity by regulating stromal pH. It was demonstrated that high envelope-bound Mg 2+ causes stromal acidification and photosynthetic inhibition. High envelope-bound Mg 2+ was also found to necessitate the activity of a digitoxinand oligomycin-sensitive ATPase for the maintenance of high stromal pH and photosynthesis in the illuminated chloroplast. In chloroplasts that had high envelope Mg 2+ and inhibited envelope ATPase activity, 2-(diethylamino)- N -(2,6-dimethylphenyl)acetamide was found to raise stromal pH and stimulate photosynthesis. 2-(Diethylamino)- N -(2,6-dimethylphenyl)acetamide is an amine anesthetic that is known to act as a monovalent cation channel blocker in mammalian systems. We postulate that the system regulating cation and H + fluxes across the plastid envelope includes a monovalent cation channel in the envelope, some degree of (envelope-bound Mg 2+ modulated) H + flux linked to monovalent cation antiport, and ATPase-dependent H + efflux.