古代TsaD-TsaC-SUA5-TcdA模块化酶的结构功能分析揭示了tRNAt6A和ct6A合成酶的原型
Mengqi Jin1, Zelin Zhang2, Zhijiang Yu1
1School of Life Sciences, Key Laboratory of Cell Activities and Stress Adaptation of the Ministry of Education, Lanzhou University, Lanzhou 730000, China.
潘多拉病毒TsaN蛋白质修改了腺酸盐,以独立于tRNA的形式形成N6-threonylcarbamoyladenosine二酸盐 (t6ADP) 和三酸盐 (t6ATP). 这种酶还将t6A核酸转化为循环t6A (ct6A),这表明tRNA修饰中的潜在祖先作用.
科学领域:
- 生物化学 生物化学
- 结构生物学 结构生物学
- 分子生物学分子生物学
背景情况:
- N 6-threonylcarbamoyladenosine (t6A) 是一个关键的tRNA修饰在位置37,对于转化忠实性和蛋白质平衡在所有生命领域至关重要.
- t6A生物合成涉及保存的蛋白家族TsaC/Sua5和TsaD/Kae1/Qri7,在细菌中通过TcdA进一步修改为循环t6A (ct6A).
研究的目的:
- 识别和表征一种新的模块化蛋白 (TsaN) 来自参与腺修饰的潘多拉病毒.
- 阐明潘多拉病毒TsaN的结构和酶活性,特别是它在t6A和ct6A形成中的作用.
主要方法:
- 使用冷电子显微镜 (cryo-EM) 确定了Pandoravirus salinus TsaN.的3.2 Å分辨率结构.
- 进行了生物化学测试,以分析TsaN在L-threonine,HCO3-,ATP和腺衍生物存在时的酶活性.
主要成果:
- TsaN的结构显示了四个域对已知t6A生物合成蛋白 (TsaD/Kae1/Qri7,TsaC/Sua5) 和TcdA.同源.
- TsaN催化了三甲基乙酸盐 (TC-AMP) 的形成,但独特的是,它继续进行tRNA独立的t6ADP和t6ATP的合成.
- TsaN还在将t6A核酸转化为ct6A方面表现出tRNA独立的活性.
结论:
- 潘多拉病毒TsaN代表了一种新的模块化酶,在腺酸修饰和ct6A形成中具有双重活性.
- TsaN的tRNA独立的催化机制表明它可能是细胞生物体中发现的祖先tRNA和ct6A修饰酶的原型.
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