Berkowitz G. A., Peters J. S.
Plant Science Department, Cook College, Rutgers-The State University of New Jersey, New Brunswick, New Jersey 08903.
Plant Physiol. 1993 May;102(1):261-267. doi: 10.1104/pp.102.1.261.
The stromal pH of the chloroplast must be maintained higher than that of the surrounding cytosol for photosynthetic carbon assimilation to occur. Experimental evidence demonstrating how this is accomplished in the plant cell is lacking. In the experiments reported here, we studied H+ and K+ flux across membranes of purified chloroplast inner-envelope vesicles. We were able to demonstrate ATP-dependent transport of both cations across the membranes of these vesicles. The data presented document the presence of an H+-pump ATPase in the chloroplast envelope. Energy-dependent K+ flux across these membranes occurs as a consequence of primary H+ pumping. The H+-pumping activity demonstrated in this report is consistent with a model involving the activity of this envelope ATPase as a primary mechanism facilitating a stroma:cytosol [delta]pH.
为了使光合碳同化发生，叶绿体的基质pH必须维持得高于周围的细胞质。目前缺乏能证明植物细胞中是如何实现这一点的实验证据。在本文所报道的实验中，我们研究了H⁺和K⁺跨纯化的叶绿体内膜囊泡膜的通量。我们能够证明这两种阳离子通过这些囊泡膜的ATP依赖型转运。所呈现的数据证明了叶绿体被膜中存在一种H⁺泵ATP酶。跨这些膜的能量依赖型K⁺通量是初级H⁺泵浦的结果。本报告中所展示的H⁺泵浦活性与一个涉及该被膜ATP酶活性作为促进基质：细胞质pH差值的主要机制的模型相一致。
