Regulation of MTK1/MEKK4 kinase activity by its N-terminal autoinhibitory domain and GADD45 binding
Regulation of MTK1/MEKK4 kinase activity by its N-terminal autoinhibitory domain and GADD45 binding
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DOI：
10.1128/mcb.22.13.4544-4555.2002
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发表时间：
2002-07-01
影响因子：
5.3
通讯作者：
Saito, H
中科院分区：
文献类型：
--
作者：
Mita, H;Tsutsui, J;Saito, H
多种细胞应激会激活应激反应性丝裂原激活蛋白 (MAP) 激酶 p38 和 JNK。在这项研究中，我们研究了人类 MA-P 激酶激酶 MTK1（也称为 MEKK4）的激活机制，它介导 p38 和 JNK 的激活。 MTK1 具有广泛的 N 末端非催化结构域，由大约 1,300 个氨基酸组成。当在酿酒酵母细胞中表达时，全长或接近全长的 MTK1 没有催化活性，就像在哺乳动物细胞中一样。删除包括位置 253 至 553 的片段会激活激酶，表明该片段包含自抑制结构域。在自抑制构象中，MTK1 激酶结构域不能与其底物 MKK6 相互作用。通过酵母细胞的功能互补筛选，GADD45 蛋白（GADD45α、β 和 γ）被鉴定为 MTK1 激活剂。 GADD45 蛋白结合 MTK1 中抑制结构域附近的位点并解除自抑制。分离出全长 MTK1 突变体，可以在缺乏激活剂 GADD45 蛋白的情况下与 MKK6 相互作用。这些 MTK1 突变体在酵母和哺乳动物细胞中都具有组成型活性。提出了 N 端抑制结构域 MTK1 自抑制和 GADD45 结合激活的模型。
A variety of cellular stresses activate the stress-responsive mitogen-activated protein (MAP) kinases p38 and JNK. In this study, we studied the activation mechanism of a human MA-P kinase kinase kinase, MTK1 (also known as MEKK4), which mediates activation of both p38 and JNK. MTK1 has an extensive N-terminal noncatalytic domain composed of similar to1,300 amino acids. Full-length or near full-length MTK1 is catalytically inactive when expressed in Saccharomyces cerevisiae cells, as it is in mammalian cells. Deletion of a segment including positions 253 to 553 activates kinase, indicating that this segment contains the autoinhibitory domain. In the autoinhibited conformation, the MTK1 kinase domain cannot interact with its substrate, MKK6. By a functional complementation screening with yeast cells, GADD45 proteins (GADD45alpha, beta, and gamma) were identified as MTK1 activators. GADD45 proteins bind a site in MTK1 near the inhibitory domain and relieve autoinhibition. Mutants of full-length MTK1 were isolated that can interact with MKK6 in the absence of the activator GADD45 proteins. These MTK1 mutants are constitutively active, in both yeast and mammalian cells. A model of MTK1 autoinhibition by the N-terminal inhibitory domain and activation by GADD45 binding is presented.