TadA，一种来自大肠杆菌的必需的tRNA特异性腺苷脱氨酶。
tadA, an essential tRNA-specific adenosine deaminase from Escherichia coli.
作者信息
Wolf Jeannette, Gerber André P, Keller Walter
机构信息
Department of Cell Biology, Biozentrum, University of Basel, CH-4056 Basel, Switzerland.
出版信息
EMBO J. 2002 Jul 15;21(14):3841-51. doi: 10.1093/emboj/cdf362.
We report the characterization of tadA, the first prokaryotic RNA editing enzyme to be identified. Escherichia coli tadA displays sequence similarity to the yeast tRNA deaminase subunit Tad2p. Recombinant tadA protein forms homodimers and is sufficient for site-specific inosine formation at the wobble position (position 34) of tRNA(Arg2), the only tRNA having this modification in prokaryotes. With the exception of yeast tRNA(Arg), no other eukaryotic tRNA substrates were found to be modified by tadA. How ever, an artificial yeast tRNA(Asp), which carries the anticodon loop of yeast tRNA(Arg), is bound and modified by tadA. Moreover, a tRNA(Arg2) minisubstrate containing the anticodon stem and loop is sufficient for specific deamination by tadA. We show that nucleotides at positions 33-36 are sufficient for inosine formation in mutant Arg2 minisubstrates. The anticodon is thus a major determinant for tadA substrate specificity. Finally, we show that tadA is an essential gene in E.coli, underscoring the critical function of inosine at the wobble position in prokaryotes.
我们报道了首个被鉴定的原核生物RNA编辑酶tadA的特性。大肠杆菌tadA与酵母tRNA脱氨酶亚基Tad2p表现出序列相似性。重组tadA蛋白形成同型二聚体，足以在tRNA（Arg2）的摆动位置（第34位）进行位点特异性肌苷形成，tRNA（Arg2）是原核生物中唯一具有这种修饰的tRNA。除了酵母tRNA（Arg）外，未发现其他真核生物tRNA底物被tadA修饰。然而，携带酵母tRNA（Arg）反密码子环的人工酵母tRNA（Asp）被tadA结合并修饰。此外，含有反密码子茎和环的tRNA（Arg2）微型底物足以被tadA进行特异性脱氨。我们表明，在突变的Arg2微型底物中，第33 - 36位的核苷酸足以形成肌苷。因此，反密码子是tadA底物特异性的主要决定因素。最后，我们表明tadA是大肠杆菌中的一个必需基因，强调了原核生物中摆动位置肌苷的关键功能。
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