A single amidotransferase forms asparaginyl-tRNA and glutaminyl-tRNA in Chlamydia trachomatis
A single amidotransferase forms asparaginyl-tRNA and glutaminyl-tRNA in Chlamydia trachomatis
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DOI：
10.1074/jbc.m109494200
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发表时间：
2001-12-07
影响因子：
4.8
通讯作者：
Söll, D
中科院分区：
文献类型：
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作者：
Raczniak, G;Becker, HD;Söll, D
氨酰-tRNA通常由氨酰-tRNA合成酶组成，这是一个20种酶的家族，对准确的蛋白质合成是必不可少的。然而，大多数细菌通过异源三聚体氨基转移酶(由GATA、GATB和GATC基因编码)催化错误充电的AsptRNA(ASN)或Gln-tRNA(GLN)的转胺化，产生两种酰胺氨酰-tRNA中的一种，Asn-tRNA或Gln-tRNA。沙眼衣原体基因组序列揭示了18个合成酶的基因，而天冬酰胺-tRNA合成酶和谷氨酰胺-tRNA合成酶的基因缺失。然而，基因组中有三个类似操纵子的gat基因(GatCAB)。我们推测衣原体使用gatCAB编码的氨基转移酶来产生Asn-tRNA和Gln-tRNA。沙眼衣原体天冬氨酰-tRNA合成酶和谷氨酰-tRNA合成酶是形成错酰化tRNA(ASN)和tRNA(Gln)的非区分性合成酶。用纯异三聚体重组沙眼衣原体氨基转移酶将Asp-tRNA(Asn)和Gln-tRNA(Gln)分别转化为Asn-tRNA和Gln-tRNA。在ATP或GTP存在的情况下，该酶使用谷氨酰胺、天冬酰胺或氨作为酰胺供体。这些结果表明，沙眼衣原体使用双重特异性的gatCAB编码的氨基转移酶和18个氨基酰-tRNA合成酶来创建一套完整的20个氨基酰-tRNA。
Aminoacyl-tRNA is generally formed by aminoacyl-tRNA synthetases, a family of 20 enzymes essential for accurate protein synthesis. However, most bacteria generate one of the two amide aminoacyl-tRNAs, Asn-tRNA or Gln-tRNA, by transamidation of mischarged AsptRNA(Asn) or Glu-tRNA(Gln) catalyzed by a heterotrimeric amidotransferase (encoded by the gatA, gatB, and gatC genes). The Chlamydia trachomatis genome sequence reveals genes for 18 synthetases, whereas those for asparaginyl-tRNA synthetase and glutaminyl-tRNA synthetase are absent. Yet the genome harbors three gat genes in an operon-like arrangement (gatCAB). We reasoned that Chlamydia uses the gatCAB-encoded amidotransferase to generate both Asn-tRNA and Gln-tRNA. C. trachomatis aspartyl-tRNA synthetase and glutamyl-tRNA synthetase were shown to be non-discriminating synthetases that form the misacylated tRNA(Asn) and tRNA(Gln) species. A preparation of pure heterotrimeric recombinant C. trachomatis amidotransferase converted Asp-tRNA(Asn) and Glu-tRNA(Gln) into Asn-tRNA and Gln-tRNA, respectively. The enzyme used glutamine, asparagine, or ammonia as amide donors in the presence of either ATP or GTP. These results suggest that C. trachomatis employs the dual specificity gatCAB-encoded amidotransferase and 18 aminoacyl-tRNA synthetases to create the complete set of 20 aminoacyl-tRNAs.