AtNOS/AtNOA1 Is a Functional Arabidopsis thaliana cGTPase and Not a Nitric-oxide Synthase
AtNOS/AtNOA1 Is a Functional Arabidopsis thaliana cGTPase and Not a Nitric-oxide Synthase
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DOI：
10.1074/jbc.m804838200
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发表时间：
2008-11-21
影响因子：
4.8
通讯作者：
Klessig, Daniel F.
中科院分区：
文献类型：
--
作者：
Moreau, Magali;Lee, Gyu In;Klessig, Daniel F.
AtNOS 1以前被确定为一个潜在的一氧化氮合酶（NOS）在拟南芥，尽管缺乏序列相似性的动物NOS。虽然Atnos 1基因敲除突变体植物的矮化和淡黄色的叶表型可以通过用外源NO处理来挽救，但最近有人怀疑AtNOS 1是否是真正的NOS。此外，根据所研究的生理反应的类型，Atnos 1并不总是缺乏NO诱导和/或检测，如先前所报道的。在这里，我们提出的实验证据表明，AtNOS 1是无法绑定和氧化精氨酸NO。这些结果支持的论点，AtNOS 1是不是一个NOS。我们还表明，重新命名的NO相关蛋白1（AtNOA 1）是循环排列的GTdR家族（cGTdR）的成员。AtNOA 1特异性地结合GTP并水解它。AtNOA 1突变体与AtNOA 1不同构建体的互补实验表明，GTP水解对于AtNOA 1的生理功能是必要的，但不是充分的。缺乏C-末端结构域的突变体AtNOA 1，虽然保留GTdR活性，但未能补充Atnoa 1，这表明该结构域在植物中起着至关重要的作用。cGTP酶似乎是RNA结合蛋白，AtNOA 1的最接近的同源物枯草芽孢杆菌YqeH已被证明参与核糖体组装和稳定性。我们提出了一个类似的功能AtNOA 1，并讨论了它在NO积累和植物发育的潜在作用。
AtNOS1 was previously identified as a potential nitric-oxide synthase (NOS) in Arabidopsis thaliana, despite lack of sequence similarity to animal NOSs. Although the dwarf and yellowish leaf phenotype of Atnos1 knock-out mutant plants can be rescued by treatment with exogenous NO, doubts have recently been raised as to whether AtNOS1 is a true NOS. Moreover, depending on the type of physiological responses studied, Atnos1 is not always deficient in NO induction and/or detection, as previously reported. Here, we present experimental evidence showing that AtNOS1 is unable to bind and oxidize arginine to NO. These results support the argument that AtNOS1 is not a NOS. We also show that the renamed NO-associated protein 1 (AtNOA1) is a member of the circularly permuted GTPase family (cGTPase). AtNOA1 specifically binds GTP and hydrolyzes it. Complementation experiments of Atnoa1 mutant plants with different constructs of AtNOA1 show that GTP hydrolysis is necessary but not sufficient for the physiological function of AtNOA1. Mutant AtNOA1 lacking the C-terminal domain, although retaining GTPase activity, failed to complement Atnoa1, suggesting that this domain plays a crucial role in planta. cGTPases appear to be RNA-binding proteins, and the closest homolog of AtNOA1, the Bacillus subtilis YqeH, has been shown to participate in ribosome assembly and stability. We propose a similar function for AtNOA1 and discuss it in the light of its potential role in NO accumulation and plant development.