Potassium collapses the Delta P in yeast mitochondria while the rate of ATP synthesis is inhibited only partially: Modulation by phosphate
Potassium collapses the Delta P in yeast mitochondria while the rate of ATP synthesis is inhibited only partially: Modulation by phosphate
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DOI：
10.1006/abbi.1997.0273
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发表时间：
1997-10-01
影响因子：
3.9
通讯作者：
Uribe, S
中科院分区：
文献类型：
--
作者：
Castrejon, V;Parra, C;Uribe, S
在0至400 μ M磷酸盐和200 μ M Mg 2+存在下，向酵母线粒体中加入浓度增加的K+，导致解偶联呼吸和质子动力（Δ P）降低：在0 K+ Δ P = 213 mV，内部为负，其中Δ psi = 180 mV和Δ pH = 33 mV，而在20 mM K+ Δ P = 28 mV，其中Δ psi = 16 mV，Δ pH = 12 mV。相反，在400 μ M Pi中，ATP的合成导致K-m和V-max的较小值，并增加ADP：在0 K+中，K-m = 18.6 μ M和V-max = 75.4 nmol（最小蛋白质）（-1），而在20 mM K+中，K-m = 5.2 μ M和V-max = 46.0 nmol（最小蛋白质）（-1），即，当K+耗尽大部分Δ P，且ADP浓度低于K-m时，ATP合成速率基本上与不存在K+时相同。在ADP饱和时，在K+存在下ATP合成的速率约为无K+时观察到的速率的60%。寡霉素或解偶联剂可抑制酵母线粒体合成ATP，K+对大鼠肝线粒体无影响。腺苷酸激酶活性在酵母线粒体中比在大鼠肝线粒体中小得多，因此不能解释在K+存在下观察到的ATP合成。增加磷酸盐浓度（1 ~ 4 mM）可阻止K ~+对酵母线粒体Δ P的影响。当磷酸盐浓度为4 mM时，Δ P始终大于200 mV，ATP合成动力学为：0 K ~+ K-m = 10.0 μ M，V-max = 88.3nmol（min.mg蛋白）（-1）。在20 mM K+时，K-m = 7.4 μ M，V-max = 133 nmol（最小值. mg蛋白质）（-1）。(C)北京：科学出版社.
Addition of increasing concentrations of K+ to yeast mitochondria in the presence of 0 to 400 mu M phosphate and 200 mu M Mg2+ led to uncoupled respiration and decreased protonmotive force (Delta P): at 0 K+ Delta P = 213 mV, negative inside, where Delta psi = 180 mV and Delta pH = 33 mV, while at 20 mM K+ Delta P = 28 mV, where Delta psi = 16 mV and Delta pH = 12 mV, In contrast, the synthesis of ATP resulted in smaller values for the K-m and the V-max in 400 mu M Pi and increasing ADP: in 0 K+, K-m = 18.6 mu M and V-max = 75.4 nmol (min.mg protein)(-1), while in 20 mM K+, K-m = 5.2 mu M and V-max = 46.0 nmol (min.mg protein)(-1), i.e., when K+ depleted most of the Delta P, and at ADP concentrations below the K-m, the rate of ATP synthesis was essentially the same as in the absence of K+. At saturating ADP, the rate of ATP synthesis in the presence of K+ was about 60% of the rate observed without K+. The synthesis of ATP by yeast mitochondria was inhibited by oligomycin or uncouplers, K+ had no effects on rat liver mitochondria. Adenylate kinase activity was much smaller in yeast mitochondria than in rat liver mitochondria and thus did not account for the synthesis of ATP observed in the presence of K+. The effects of K+ on the Delta P of yeast mitochondria were prevented by increasing concentrations of phosphate (1 to 4 mM), At 4 mM phosphate, the Delta P was always above 200 mV and the kinetics of ATP synthesis were as follows: 0 K+ K-m = 10.0 mu M and V-max = 88.3 nmol (min.mg protein)(-1). At 20 mM K+, K-m = 7.4 mu M and V-max = 133 nmol (min.mg protein)(-1). (C) 1997 Academic Press.