Nakamura Akiyoshi, Yao Min, Chimnaronk Sarin, Sakai Naoki, Tanaka Isao
Faculty of Advanced Life Sciences, Hokkaido University, Sapporo 060-0810, Japan.
Science. 2006 Jun 30;312(5782):1954-8. doi: 10.1126/science.1127156.
The formation of glutaminyl transfer RNA (Gln-tRNA(Gln)) differs among the three domains of life. Most bacteria employ an indirect pathway to produce Gln-tRNA(Gln) by a heterotrimeric glutamine amidotransferase CAB (GatCAB) that acts on the misacylated Glu-tRNA(Gln). Here, we describe a series of crystal structures of intact GatCAB from Staphylococcus aureus in the apo form and in the complexes with glutamine, asparagine, Mn2+, and adenosine triphosphate analog. Two identified catalytic centers for the glutaminase and transamidase reactions are markedly distant but connected by a hydrophilic ammonia channel 30 A in length. Further, we show that the first U-A base pair in the acceptor stem and the D loop of tRNA(Gln) serve as identity elements essential for discrimination by GatCAB and propose a complete model for the overall concerted reactions to synthesize Gln-tRNA(Gln).
谷氨酰胺转移核糖核酸（Gln - tRNA(Gln)）的形成在生命的三个域中有所不同。大多数细菌通过一种异源三聚体谷氨酰胺酰胺转移酶CAB（GatCAB）采用间接途径来产生Gln - tRNA(Gln)，该酶作用于错误酰化的Glu - tRNA(Gln)。在此，我们描述了来自金黄色葡萄球菌的完整GatCAB在无配体形式以及与谷氨酰胺、天冬酰胺、Mn2 +和三磷酸腺苷类似物形成复合物时的一系列晶体结构。确定的谷氨酰胺酶和转氨甲酰酶反应的两个催化中心相距甚远，但由一个长度为30埃的亲水性氨通道相连。此外，我们表明tRNA(Gln)受体茎中的第一个U - A碱基对和D环作为GatCAB进行识别所必需的识别元件，并提出了一个完整的总体协同反应模型来合成Gln - tRNA(Gln)。
