Dynamic function of the alkyl spacer of acetogenins in their inhibitory action with mitochondrial complex I (NADH-ubiquinone oxidoreductase)
Dynamic function of the alkyl spacer of acetogenins in their inhibitory action with mitochondrial complex I (NADH-ubiquinone oxidoreductase)
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DOI：
10.1021/bi051568t
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发表时间：
2005-11-15
期刊：
影响因子：
2.9
通讯作者：
Miyoshi, H
中科院分区：
文献类型：
--
作者：
Abe, M;Murai, M;Miyoshi, H
乙酰配基是线粒体功能复合物I（NADH-泛醌氧化还原酶）最强的抑制剂，对其抑制机制的研究有助于阐明该酶末端电子传递步骤的结构和特征。先前的结构-活性关系的研究表明，除了连接两个毒性基团的烷基间隔基（即，羟基化的THF和γ-内酯环），这些抑制剂的多个官能团中没有一个是有效抑制所必需的。为了阐明烷基间隔基的功能，合成了两组系统选择的类似物。首先，间隔物的长度变化很大。第二，通过在间隔物的不同区域中引入多个键来具体地降低间隔物的局部柔性。用于抑制的间隔基的最佳长度为约13个碳原子。从13个碳延长间隔子引起的抑制作用强度的降低比缩短引起的抑制作用强度的降低剧烈得多。间隔区特定区域的局部柔性对抑制作用并不重要。这些观察结果表明，间隔区的活性构象不是延伸形式，并且不一定限于某种刚性形状。此外，其中覆盖10个碳原子的间隔物硬化成棒状形状的类似物仍然保持有效的抑制作用。我们的研究结果强烈表明，间隔区部分是免费的空间拥挤所产生的推定的结合位点可能是因为没有空腔样的结合位点的间隔区部分。结合酶的方式可能无法解释一个简单的“钥匙和锁孔”的类比。
Studies on the inhibitory mechanism of acetogenins, the most potent inhibitors of mitochondrial functional complex I (NADH-ubiquinone oxidoreductase), are useful for elucidating the structural and features of the terminal electron transfer step of this enzyme. Previous studies of the structure-activity relationship revealed that except for the alkyl spacer linking the two toxophores (i.e., the hydroxylated THF and the gamma-lactone rings), none of the multiple functional groups of these inhibitors is essential for potent inhibition. To elucidate the function of the alkyl spacer, two sets of systematically selected analogues were synthesized. First, the length of the spacer was varied widely. Second, the local flexibility of the spacer was specifically reduced by introducing multiple bond(s) into different regions of the spacer. The optimal length of the spacer for inhibition was approximately 13 carbon atoms. The decrease in the strength of the inhibitory effect caused by elongating the spacer from 13 carbons was much more drastic than that caused by shortening. Local flexibility in a specific region of the spacer was not important for the inhibition. These observations indicate that the active conformation,of the spacer is not an extended form, and is not necessarily restricted to a certain rigid shape. Moreover, an analogue in which a spacer covering 10 carbon atoms was hardened into a rodlike shape still maintained a potent inhibitory effect. Our results strongly suggest that the spacer portion is free from steric congestion arising from the putative binding site probably because there is no cavity-like binding site for the spacer portion. The manner of acetogenin binding to the enzyme may not be explained by a simple "key and keyhole" analogy.