Two types of ammonium uncoupling in pea chloroplasts

• Published in: Biochemistry (Moscow) Vol. 75; no. 6; pp. 784 - 791
• Main Authors: Opanasenko, V. K, Vasyukhina, L. A, Naydov, I. A
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : SP MAIK Nauka/Interperiodica 01.06.2010; SP MAIK Nauka/Interperiodica; Springer; Springer Nature B.V
• Subjects: Adenosine triphosphatase; Adenosine Triphosphate - biosynthesis; Ammonia; Ammonium; Biochemistry; Biomedical and Life Sciences; Biomedicine; Bioorganic Chemistry; Cellular biology; Chloroplasts - metabolism; Cytokinins; Electron Transport; Fatty acids; Fluorescent Dyes - chemistry; Hydrogen; Hydrogen ions; Legumes; Life Sciences; Microbiology; Palmitic Acid - pharmacology; Peas; Pisum sativum - metabolism; Quaternary Ammonium Compounds - pharmacology; Rhodamines - chemistry; ATP synthesis; chloroplasts; ion regulation; ammonium uncoupling; electron transfer; DCCD
• ISSN: 0006-2979; 1608-3040
• DOI: 10.1134/S0006297910060143

The effect of ammonium on ATP synthesis, electron transfer, and light-induced uptake of hydrogen ions in pea chloroplasts was studied. It is shown that the dependence of these reactions on ammonium concentration could be due to effects of two different uncoupling processes. The first process is induced by low ammonium concentrations (<0.2 mM); the second one is observed in the NH₄Cl concentration interval of 0.5-5.0 mM. The first type of uncoupling is stimulated by palmitic acid or by N,N′-dicyclohexylcarbodiimide, while the second is stimulated by chloroplast thylakoid swelling caused by energy-dependent osmotic gradients. In the presence of the fluorescent dye sulforhodamine B, which does not penetrate through the cell membrane, this swelling causes the dye to enter the lumens. It is supposed that ammonium activates two different routes of cation leakage from the lumen. The first route involves channel proteins, while the second is a mechanosensitive pore that opens in response to osmotic gradients.