Crystal structures of the clock protein EA4 from the silkworm Bombyx mori
Crystal structures of the clock protein EA4 from the silkworm Bombyx mori
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DOI：
10.1016/j.jmb.2008.01.020
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发表时间：
2008-03-28
影响因子：
5.6
通讯作者：
Park, Sam-Yong
中科院分区：
文献类型：
--
作者：
Hiraki, Toshiki;Shibayama, Naoya;Park, Sam-Yong
许多昆虫在被称为滞育的受阻发育阶段度过冬天，滞育要么是卵，要么是蛹，甚至是成虫。要在春季从滞育中苏醒，就需要暴露在漫长的冬季寒冷中。在家蚕滞育卵中，一种金属糖蛋白EA4(EA4)被认为是冷时钟，因为其特有的ATPase活性在必要的冷期结束时瞬间升高。已知EA4的这种计时器特性始于冷条件下抑制肽(称为肽抑制针)的解离，但其计时机制完全未知。在这里，我们介绍了EA4的晶体结构和功能特性，包括糖基化和非糖基化。我们发现EA4是一个同源二聚体ATPase，每个亚基由一个铜锌超氧化物歧化酶折叠组成。有一个额外的短N-末端区域能够与另一个铜离子结合，这表明该离子参与了计时机制。糖链似乎加强了肽抑制针的结合，这可能反过来稳定N-末端结构域的初始构象，解释糖基化和肽设定时钟的要求。(C)2008爱思唯尔有限公司。保留所有权利。
Many insects pass the winter in an arrested developmental stage called diapause, either as eggs, as pupae, or even as adults. Exposure to the prolonged cold of winter is required to permit awakening from diapause in the spring. In the diapause eggs of the silkworm Bombyx mori, a metalloglycoprotein, esterase A4 (EA4), has been suggested to serve as a cold-duration clock because its characteristic ATPase activity is transiently elevated at the end of the necessary cold period. This timer property of EA4 is known to start with the dissociation of an inhibitory peptide (called "peptidyl inhibitory needle") under cold conditions, but its time-measuring mechanism is completely unknown. Here we present the crystal structures and functional properties of EA4 with and without glycosylation. We show that EA4 is a homodimeric ATPase, with each subunit consisting of a copper-zinc superoxide dismutase fold. There is an additional short N-terminal region that is capable of binding one more copper ion, suggesting a timer mechanism in which this ion is involved. The sugar chain appears to reinforce the binding of peptidyl inhibitory needle, which may in turn stabilize the initial conformation of the N-terminal domain, explaining the requirement for glycosylation and for the peptide to set the clock. (C) 2008 Elsevier Ltd. All rights reserved.