Sampling the conformational space of the catalytic subunit of human γ-secretase
Sampling the conformational space of the catalytic subunit of human γ-secretase
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DOI：
10.7554/elife.11182
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发表时间：
2015-12-01
期刊：
影响因子：
7.7
通讯作者：
Scheres, Sjors H. W.
中科院分区：
文献类型：
--
作者：
Bai, Xiao-chen;Rajendra, Eeson;Scheres, Sjors H. W.
人γ分泌酶是一种膜内蛋白酶，可裂解许多不同的底物。Notch的异常切割与癌症有关，而淀粉样蛋白前体蛋白的异常切割可导致阿尔茨海默病。我们之前的γ -分泌酶的低温电镜结构显示其催化亚基早老素有相当大的紊乱。在这里，我们描述了一种在二级结构水平上表征分子可塑性的图像分类程序，并应用该方法在我们之前的样品中识别出三种不同的构象。在其中一种构象中，可以看到一个额外的跨膜螺旋，它不能归因于已知的分泌酶成分。此外，我们提出了一个与二肽抑制剂N-[N-（3,5-二氟苯乙酰基）- l -丙氨基]- s -苯基甘氨酸t-丁基酯（DAPT）配合的γ分泌酶结构。我们的研究结果揭示了早老素的第二和第六跨膜螺旋的构象迁移率如何在DAPT或其他螺旋结合时大大降低，并为底物如何进入跨膜结构域的新模型奠定了基础。DOI: 10.7554 / eLife.11182.001
Human gamma-secretase is an intra-membrane protease that cleaves many different substrates. Aberrant cleavage of Notch is implicated in cancer, while abnormalities in cutting amyloid precursor protein lead to Alzheimer's disease. Our previous cryo-EM structure of gamma-secretase revealed considerable disorder in its catalytic subunit presenilin. Here, we describe an image classification procedure that characterizes molecular plasticity at the secondary structure level, and apply this method to identify three distinct conformations in our previous sample. In one of these conformations, an additional transmembrane helix is visible that cannot be attributed to the known components of gamma-secretase. In addition, we present a gamma-secretase structure in complex with the dipeptidic inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT). Our results reveal how conformational mobility in the second and sixth transmembrane helices of presenilin is greatly reduced upon binding of DAPT or the additional helix, and form the basis for a new model of how substrate enters the transmembrane domain. DOI:10.7554/eLife.11182.001