On the mechanism of sulfite activation of chloroplast thylakoid ATPase and the relation of ADP tightly bound at a catalytic site to the binding change mechanism.
On the mechanism of sulfite activation of chloroplast thylakoid ATPase and the relation of ADP tightly bound at a catalytic site to the binding change mechanism.
复制标题
叶绿体类囊体ATP酶亚硫酸盐活化机制及催化位点紧密结合的ADP与结合变化机制的关系。
DOI：
10.1021/bi00454a014
复制
发表时间：
1990
期刊：
影响因子：
2.9
通讯作者：
Boyer,PD
中科院分区：
文献类型：
--
作者：
Du,ZY;Boyer,PD
摘要：经洗涤的叶绿体类囊体膜暴露于[3 H] ADP后，在ATP合酶的催化位点上保留了紧密结合的[3 H] ADP。足够的内源性或添加的Mg 2+的存在导致酶基本上没有ATP酶活性。亚硫酸盐激活ATP酶，并且在大多数结合的[3 H] ADP被释放之前，每个合酶的许多ATP分子可以被水解，该结果被解释为表明ADP在参与亚硫酸盐激活的酶的催化的位点处不被结合[Larson，E. M.，Umbach，A.，& Jenjorf，A. T.（1989）生物化学。Biophys. Acta 973，75-85]。我们提出的证据表明，情况并非如此。当暴露于MgATP和20-100 mM亚硫酸盐时，Mg 2+和ADP抑制的酶在达到与未被Mg 2+和ADP抑制的光激活ATP酶相同的稳态速率之前，在22 ℃下显示出约1分钟的滞后，在37 ℃下显示出约15秒的滞后。如果在加入MgATP之前将酶暴露于亚硫酸盐，则延迟不会消除，这表明ATP酶周转对于活化是必要的。大多数结合的[3 H] ADP的释放与ATP酶活性的开始平行，尽管一些[3 H] ADP即使在延长的催化周转时间下也不释放，并且可能在活性差或无活性的酶上或在非催化位点上。结果是一致的，大多数紧密结合的[3 H] ADP是在一个催化位点，并被取代，因为这个Mg 2+和ADP抑制网站重新获得等同的参与与其他催化位点上的活化酶。亚硫酸盐的激活作用可以解释为亚硫酸盐在酶-ADP-Mg ~（2+）复合物的P ~+结合位点结合，形成一种更容易被ATP在另一个位点结合而激活的形式。
Revised Manuscript Received July 17, 1989 abstract: Washed chloroplast thylakoid membranes uponexposure to [3H] ADP retain a tightly bound [3H] ADP on a catalytic site of the ATP synthase. The presence of sufficient endogenous or added Mg2+ results in an enzyme with essentially no ATPase activity. Sulfite activates the ATPase, and many molecules of ATP per synthase can be hydrolyzed before most of the bound [3H] ADP is released, a result interpreted as indicating that the ADP is not bound at a site participating incatalysis by the sulfite-activated enzyme [Larson, E. M., Umbach, A., & Jagendorf, A. T.(1989) Biochim. Biophys. Acta 973, 75-85]. We present evidence that this is not the case. The Mg2+-and ADP-inhibited enzyme when exposed to MgATP and 20-100 mM sulfite shows a lag of about 1 min at 22 C and of about 15 s at 37 C before reaching the same steady-state rate as attained with light-activated ATPase that has not been inhibited by Mg2+ and ADP. Thelag is not eliminated if the enzyme is exposed to sulfite prior to MgATP addition, indicating that ATPaseturnover is necessary for the activation. The release of most of the bound [3H] ADP parallels the onset of ATPase activity, although some [3H] ADP is not released even with prolonged catalytic turnover and may be on poorly active or inactive enzyme or at noncatalytic sites. The results are consistent with most of the tightly bound [3H] ADP being at a catalytic site and being replaced as this Mg2+-and ADP-inhibited site regains equivalent participation with other catalytic sites on the activated enzyme. The sulfite activation can be explained by sulfite combination at a P¡ binding site of the enzyme-ADP-Mg2+ complex to give a form more readily activated by ATP binding at an alternative site.