Institute of Fundamental Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, Russia.
Biochemistry (Mosc). 2010 Jun;75(6):784-91. 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 NH(4)Cl 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.
研究了铵对豌豆叶绿体中 ATP 合成、电子传递和光诱导氢离子摄取的影响。结果表明，这些反应对铵浓度的依赖性可能归因于两种不同解耦过程的影响。第一种解耦过程是由低浓度的铵（<0.2mM）诱导的；第二种则在 NH4Cl 浓度区间 0.5-5.0mM 内观察到。第一种解耦类型由棕榈酸或 N,N'-二环己基碳二亚胺刺激，而第二种则由叶绿体类囊体肿胀引起，这种肿胀是由能量依赖性渗透梯度引起的。在荧光染料 sulforhodamine B 的存在下，该染料不会穿透细胞膜，这种肿胀会导致染料进入腔室。据推测，铵激活了从腔室中阳离子漏出的两种不同途径。第一条途径涉及通道蛋白，而第二条途径是机械敏感的孔，它会响应渗透梯度而打开。
