Stoichiometry of proton movements coupled to ATP synthesis driven by a pH gradient in Streptococcus lactis.
Stoichiometry of proton movements coupled to ATP synthesis driven by a pH gradient in Streptococcus lactis.
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乳酸链球菌中由 pH 梯度驱动的质子运动与 ATP 合成耦合的化学计量。
DOI：
10.1007/bf01868482
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发表时间：
1982
期刊：
影响因子：
--
通讯作者：
Hansen3rd,FC
中科院分区：
文献类型：
--
作者：
Maloney,PC;Hansen3rd,FC
通过向悬浮在pH 8的磷酸钾中的细胞中加入硫酸沿着缬氨霉素或渗透性阴离子，建立了H+穿过厌氧乳酸链球菌质膜的电化学电势差。通过水杨酸的分布来测量随后的细胞酸化。用抑制剂N，N′-二环己基碳二亚胺处理或未处理的细胞之间的比较用于揭示净质子进入的部分可归因于H+流入和由该微生物的可逆质子转运ATP酶催化的ATP合成之间的直接偶联。当施加的电化学质子梯度低于180-190 mV时，对于对照细胞和用ATP酶抑制剂处理的细胞，质子进入以预期的被动通量速率进行。然而，在较高的驱动力的控制细胞的酸化显着加速，与ATP的合成一致，而酸化的抑制剂处理的细胞继续以被动流入的速率特性。该观察到的阈值（180-190 mV）被确定为该H+“泵”的逆转电位。平行测量表明，在这些洗涤过的细胞中ATP的水解自由能为8.4千卡/摩尔（370毫伏）。的反转（阈值）电位和ATP的水解自由能之间的比较表明，2 H+/ATP的化学计量的质子运动的耦合，在细菌中ATP的形成。
An electrochemical potential difference for H+was established across the plasma membrane of the anaerobeStreptococcus lactisby addition of sulfuric acid to cells suspended in potassium phosphate at pH 8 along with valinomycin or permeant anions. Subsequent acidification of the cell was measured by the distribution of salicyclic acid. A comparison between cells treated or untreated with the inhibitor N,N′-dicyclohexylcarbodiimide was used to reveal that portion of net proton entry attributable to a direct coupling between H+inflow and synthesis of ATP catalyzed by the reversible proton-translocating ATPase of this microorganism. When the imposed electrochemical proton gradient was below 180–190 mV, proton entry was at the rate expected of passive flux, for both control cells and cells treated with the ATPase inhibitor. However, at higher driving force acidification of control cells was markedly accelerated, coincident with ATP synthesis, while acidification of cells treated with the inhibitor continued at the rate characteristic of passive inflow. This observed threshold (180–190 mV) was identified as the reversal potential for this H+“pump”. Parallel measurements showed that the free energy of hydrolysis for ATP in these washed cells was 8.4 kcal/mole (370 mV). The comparison between the reversal (threshold) potential and the free energy of hydrolysis for ATP indicates a stoichiometry of 2 H+/ATP for the coupling of proton movements to ATP formation in bacteria.