Lippe G, Sorgato M C, Harris D A
Institute of Biochemistry, University of Padova, Italy.
Biochim Biophys Acta. 1988 Mar 30;933(1):12-21. doi: 10.1016/0005-2728(88)90051-5.
(1) The effects of membrane potential (delta psi) and nucleotides on the interaction between the F1-ATP synthase and its natural inhibitor protein (IF1) are studied in ox-heart submitochondrial vesicles. (2) Membrane potential causes displacement of IF1 from submitochondrial vesicles, as shown by measuring both delta psi-dependent stimulation of ATPase capacity and release of 125I-labelled IF1 from the vesicles. These effects are abolished if ATP is included in the incubation. (3) There is a linear increase in the steady-state ATPase capacity of oxidising vesicles as delta psi is increased from 100 mV to 135 mV. Increasing delta psi above 140 mV leads to no further change. (4) At a constant membrane potential, ATP suppresses the increase in ATPase capacity, with a concentration for half maximal effect of 140 microM. This value is close to the Km for ATP hydrolysis by membrane-bound F1. This suppression is related to ATP concentration rather than to delta Gp or ATP/ADP ratio. (5) The unidirectional on- and off-rates of IF1 were measured separately. The off-rate of IF1 is increased by membrane potential but unaffected by ATP. The on-rate, conversely, is increased by ATP. Thus, the suppression of the potential-dependent net release of IF1 from submitochondrial vesicles by ATP results from an increase of the IF1 on-rate above the off-rate.
（1）在牛心亚线粒体囊泡中研究了膜电位（Δψ）和核苷酸对F1-ATP合酶与其天然抑制蛋白（IF1）之间相互作用的影响。（2）膜电位导致IF1从亚线粒体囊泡中移位，这通过测量依赖于Δψ的ATP酶活性刺激以及从囊泡中释放125I标记的IF1来表明。如果在孵育中加入ATP，这些效应就会被消除。（3）随着Δψ从100mV增加到135mV，氧化囊泡的稳态ATP酶活性呈线性增加。将Δψ增加到140mV以上不会导致进一步变化。（4）在恒定的膜电位下，ATP抑制ATP酶活性的增加，半最大效应浓度为140μM。该值接近膜结合F1水解ATP的Km值。这种抑制与ATP浓度有关，而不是与ΔGp或ATP/ADP比值有关。（5）分别测量了IF1的单向结合和解离速率。IF1的解离速率因膜电位而增加，但不受ATP影响。相反，结合速率因ATP而增加。因此，ATP对IF1从亚线粒体囊泡中依赖电位的净释放的抑制是由于IF1结合速率增加到解离速率之上所致。
