REGULATION OF THE RECONSTITUTED CHLOROPLAST PHOSPHATE TRANSLOCATOR BY AN H+ GRADIENT
REGULATION OF THE RECONSTITUTED CHLOROPLAST PHOSPHATE TRANSLOCATOR BY AN H+ GRADIENT
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DOI：
10.1016/0005-2728(83)90195-0
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发表时间：
1983-01-01
期刊：
影响因子：
--
通讯作者：
HELDT, HW
中科院分区：
文献类型：
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作者：
FLUGGE, UI;GERBER, J;HELDT, HW
该报告描述了 ΔpH 对重构系统中磷酸转运蛋白催化的磷酸盐、磷酸丙糖和 3-磷酸甘油酸转运的影响。通过添加外部缓冲溶液来调节穿过脂质体膜的H+梯度并维持几分钟。获得以下结果： (1)向内定向的H+梯度导致3-磷酸甘油酸转运增加以及磷酸盐和磷酸丙糖转运减少。 (2) 相反方向的 H+ 梯度导致 3-磷酸甘油酸流入受到限制，而磷酸盐和磷酸丙糖的流入则得到增强。 (3) pH 效应的大小取决于内部底物。与同质交换模式相比，异质交换模式中施加 ΔpH 的影响更为明显。 (4) 磷酸盐和3-磷酸甘油酸的运输受ΔpH以不同的方式影响。在磷酸盐和磷酸丙糖转运的情况下，观察到的效果与表观Km值的变化相关，而在3-磷酸甘油酸转运的情况下，pH梯度的应用与Vmax的变化相关。 (5) 在外部介质中两种底物的竞争实验中，ΔpH 影响磷酸盐作为 3-磷酸甘油酸转运竞争性抑制剂的作用，而 3-磷酸甘油酸对磷酸盐转运的作用不受 pH 梯度的影响。 (6) 在 ΔpH 影响下测得的表观 Kman 和 Vmax 值可用于计算照明期间穿过包络线的底物通量。可以证明，光下基质pH值的增加会引起转运底物比例的显着变化。在没有pH梯度的条件下，运出的物质主要是3-磷酸甘油酸，运入的物质主要是磷酸丙糖。当施加 pH 梯度（光照条件）时，这些通量会反转。
This report describes the influence of ΔpH on the transport of phosphate, triose phosphate and 3-phosphoglycerate catalyzed by the phosphate translocator in a reconstituted system. The H+gradient across the liposome membrane is adjusted by the addition of external buffer solution and maintained for several minutes. The following results are obtained: (1) An inward directed H+gradient leads to an increase of 3-phosphoglycerate transport and to a decrease of phosphate and triose phosphate transport. (2) An H+gradient in the opposite direction results in a restriction of 3-phosphoglycerate influx whereas the influx of phosphate and triose phosphate is enhanced. (3) The magnitude of the pH effect depends on the internal substrate. Compared to the homoexchange mode, the effect of applied ΔpH is more pronounced in the heteroexchange mode. (4) Transport of phosphate and 3-phosphoglycerate is influenced by ΔpH in a different manner. In the case of phosphate and triose phosphate transport the observed effects are associated with changes in the apparentKmvalues whereas in the case of 3-phosphoglycerate transport the application of a pH gradient is linked to a change ofVmax. (5) In competition experiments with both substrates in the external medium, ΔpH influences the effect of phosphate as a competitive inhibitor of 3-phosphoglycerate transport whereas the effect of 3-phosphoglycerate on phosphate transport is not affected by a pH gradient. (6) The measured apparentKmandVmaxvalues under the influence of ΔpH can be used for the calculation of substrate fluxes across the envelope during illumination. It can be demonstrated that the increase of stromal pH in the light gives rise to a considerable change in the ratio of the substrates transported. Under conditions without pH gradient, the species transported out is mainly 3-phosphoglycerate and the species transported in is mainly triose phosphate. These fluxes are reversed when a pH gradient is applied (light conditions).