Contribution of Presenilin Transmembrane Domains 6 and 7 to a Water-containing Cavity in the γ-Secretase Complex*
Contribution of Presenilin Transmembrane Domains 6 and 7 to a Water-containing Cavity in the γ-Secretase Complex*
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早老素跨膜结构域 6 和 7 对 γ-分泌酶复合物中含水空腔的贡献*
DOI：
10.1074/jbc.m604997200
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发表时间：
2006
影响因子：
4.8
通讯作者：
B. de Strooper
中科院分区：
文献类型：
--
作者：
A. Tolia;L. Chávez;B. de Strooper
γ-分泌酶是一种多蛋白复合物，负责淀粉样蛋白前体蛋白和其他I型跨膜蛋白的膜内裂解。早老素（该复合物的催化核心）的突变会导致阿尔茨海默病。人们对该蛋白的结构知之甚少，对其催化机制更是知之甚少，其催化机制涉及在细胞膜疏水环境下的蛋白水解裂解。目前还不清楚水解所需的水是如何提供给这个反应的。在这方面，早老素跨膜结构域6和7似乎是关键的，因为每个结构域都有一个关键的天冬氨酸，有助于催化活性。目前的模型表明，这两个天冬氨酸基团应该是紧密对立的，并且可以接触到水。然而，这还有待实验验证。在这里，我们对这两个结构域进行了半胱氨酸扫描诱变，并证明了一些引入的残基暴露于水中，为早老素的催化核心中存在充满水的空腔提供了实验证据。此外，我们已经证明了两种天冬氨酸存在于这个空腔中，并且在天然复合体中彼此相对。我们还确定了保守的酪氨酸389作为催化机制的关键伙伴。一些额外的氨基酸取代对γ-分泌酶底物的处理有不同的影响，这意味着它们有助于酶的特异性。我们的数据表明，有可能设计出更具选择性的γ-分泌酶抑制剂。
γ-Secretase is a multiprotein complex responsible for the intramembranous cleavage of the amyloid precursor protein and other type I transmembrane proteins. Mutations in Presenilin, the catalytic core of this complex, cause Alzheimer disease. Little is known about the structure of the protein and even less about the catalytic mechanism, which involves proteolytic cleavage in the hydrophobic environment of the cell membrane. It is basically unclear how water, needed to perform hydrolysis, is provided to this reaction. Presenilin transmembrane domains 6 and 7 seem critical in this regard, as each bears a critical aspartate contributing to catalytic activity. Current models imply that both aspartyl groups should closely oppose each other and have access to water. This is, however, still to be experimentally verified. Here, we have performed cysteine-scanning mutagenesis of both domains and have demonstrated that several of the introduced residues are exposed to water, providing experimental evidence for the existence of a water-filled cavity in the catalytic core of Presenilin. In addition, we have demonstrated that the two aspartates reside within this cavity and are opposed to each other in the native complex. We have also identified the conserved tyrosine 389 as a critical partner in the catalytic mechanism. Several additional amino acid substitutions affect differentially the processing of γ-secretase substrates, implying that they contribute to enzyme specificity. Our data suggest the possibility that more selective γ-secretase inhibitors could be designed.
有证据表明人早老素 1 的 COOH 末端位于胞质外空间。
DOI：
10.1152/ajpcell.00636.2004
发表时间：
2005
期刊：
American journal of physiology. Cell physiology
影响因子：
--
作者：
Oh,YoungS;Turner,RJames
通讯作者：
Turner,RJames
DOI：
10.1073/pnas.97.11.5796
发表时间：
2000-05-23
影响因子：
11.1
作者：
Eilers, M;Shekar, SC;Fleming, PJ
通讯作者：
Fleming, PJ