Crystal Structure of Epiphyas postvittana Takeout 1 with Bound Ubiquinone Supports a Role as Ligand Carriers for Takeout Proteins in Insects
Crystal Structure of Epiphyas postvittana Takeout 1 with Bound Ubiquinone Supports a Role as Ligand Carriers for Takeout Proteins in Insects
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DOI：
10.1074/jbc.m807467200
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发表时间：
2009-02-06
影响因子：
4.8
通讯作者：
Newcomb, Richard D.
中科院分区：
文献类型：
--
作者：
Hamiaux, Cyril;Stanley, Duncan;Newcomb, Richard D.
外卖（To）蛋白只存在于昆虫中，并被认为在昆虫的生理和行为的各个方面起着重要作用。与鳞翅目幼体激素结合蛋白（JHBPs）的有限序列相似性表明，To蛋白在结合疏水配体中起作用。我们首次从浅棕色苹果蛾Epiphyas postvittana中获得了To蛋白EpTo1的晶体结构，并利用硫异常色散的单波长异常衍射技术进行了内部解析，并将其细化到1.3埃分辨率。EpTo1采用不寻常的α / β包裹折叠，仅在JHBP和几种哺乳动物脂质载体蛋白中可见，这是一种专门用于结合和/或运输疏水配体的支架。EpTo1有一个45埃长的纯疏水性内部通道，延伸到蛋白质的整个长度，并容纳一个结合的配体。后者经质谱分析为泛素-8，可能来源于大肠杆菌。该结构提供了第一个直接的实验证据，证明To蛋白是配体载体；揭示了EpTo1内源性配体的性质；通过与JHBP的比较，显示出不同配体特异性的基础；并提出了一种结合/释放配体的机制。
Takeout (To) proteins are found exclusively in insects and have been proposed to have important roles in various aspects of their physiology and behavior. Limited sequence similarity with juvenile hormone-binding proteins (JHBPs), which specifically bind and transport juvenile hormones in Lepidoptera, suggested a role for To proteins in binding hydrophobic ligands. We present the first crystal structure of a To protein, EpTo1 from the light brown apple moth Epiphyas postvittana, solved in-house by the single-wavelength anomalous diffraction technique using sulfur anomalous dispersion, and refined to 1.3 angstrom resolution. EpTo1 adopts the unusual alpha/beta-wrap fold, seen only for JHBP and several mammalian lipid carrier proteins, a scaffold tailored for the binding and/or transport of hydrophobic ligands. EpTo1 has a 45 angstrom long, purely hydrophobic, internal tunnel that extends for the full length of the protein and accommodates a bound ligand. The latter was shown by mass spectrometry to be ubiquinone-8 and is probably derived from Escherichia coli. The structure provides the first direct experimental evidence that To proteins are ligand carriers; gives insights into the nature of endogenous ligand(s) of EpTo1; shows, by comparison with JHBP, a basis for different ligand specificities; and suggests a mechanism for the binding/release of ligands.