Molecular mechanism for regulation of the human mitochondrial branched-chain alpha-ketoacid dehydrogenase complex by phosphorylation.
Molecular mechanism for regulation of the human mitochondrial branched-chain alpha-ketoacid dehydrogenase complex by phosphorylation.
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DOI：
10.1016/j.str.2004.09.013
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发表时间：
2004-12
期刊：
影响因子：
5.7
通讯作者：
R. Wynn;Masato Kato;M. Machius;J. Chuang;Jun Li;D. Tomchick;D. Chuang
中科院分区：
文献类型：
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作者：
R. Wynn;Masato Kato;M. Machius;J. Chuang;Jun Li;D. Tomchick;D. Chuang
人线粒体支链α-酮酸脱氢酶复合体是一个由三个催化组分(E1b、E2b和E3)、一个激酶和一个磷酸酶组成的4MDA型大分子机器。BCKDC的整体活性受到激素和饮食刺激的磷酸化的严格调控。我们报道，在E1b活性部位通道中Ser292-α的磷酸化导致携带磷酸化丝氨酸的保守的磷酸化环路的有序到无序的转变。构象变化是由磷酸基与不变的His291-α发生空间碰撞而触发的，His291-His291是通过结合的硫胺素二磷酸作为磷酸化环不可或缺的锚。Ser292-α的磷酸化不会严重阻碍E1b依赖的α-酮酸的脱羧化。然而，无序的环状构象阻止了磷酸化的E1b与E2b硫酰基结构域结合，从而有效地关闭了E1b催化的还原酰化反应，从而完全灭活了BCKDC。这一机制为通过磷酸化调控线粒体α-酮酸脱氢酶复合体提供了范例。
The human mitochondrial branched-chain α-ketoacid dehydrogenase complex (BCKDC) is a 4 MDa macromolecular machine comprising three catalytic components (E1b, E2b, and E3), a kinase, and a phosphatase. The BCKDC overall activity is tightly regulated by phosphorylation in response to hormonal and dietary stimuli. We report that phosphorylation of Ser292-α in the E1b active site channel results in an order-to-disorder transition of the conserved phosphorylation loop carrying the phosphoryl serine. The conformational change is triggered by steric clashes of the phosphoryl group with invariant His291-α that serves as an indispensable anchor for the phosphorylation loop through bound thiamin diphosphate. Phosphorylation of Ser292-α does not severely impede the E1b-dependent decarboxylation of α-ketoacids. However, the disordered loop conformation prevents phosphorylated E1b from binding the E2b lipoyl-bearing domain, which effectively shuts off the E1b-catalyzed reductive acylation reaction and therefore completely inactivates BCKDC. This mechanism provides a paradigm for regulation of mitochondrial α-ketoacid dehydrogenase complexes by phosphorylation.