Sievers Katharina, Neumann Piotr, Sušac Lukas, Da Vela Stefano, Graewert Melissa, Trowitzsch Simon, Svergun Dmitri, Tampé Robert, Ficner Ralf
Department of Molecular Structural Biology, GZMB, University of Göttingen, 37077 Göttingen, Germany.
Institute of Biochemistry, Biocenter, Goethe University Frankfurt, 60438 Frankfurt/Main, Germany.
Structure. 2024 Mar 7;32(3):316-327.e5. doi: 10.1016/j.str.2023.12.006. Epub 2024 Jan 4.
Eukaryotic tRNA guanine transglycosylase (TGT) is an RNA-modifying enzyme which catalyzes the base exchange of the genetically encoded guanine 34 of tRNAs for queuine, a hypermodified 7-deazaguanine derivative. Eukaryotic TGT is a heterodimer comprised of a catalytic and a non-catalytic subunit. While binding of the tRNA anticodon loop to the active site is structurally well understood, the contribution of the non-catalytic subunit to tRNA binding remained enigmatic, as no complex structure with a complete tRNA was available. Here, we report a cryo-EM structure of eukaryotic TGT in complex with a complete tRNA, revealing the crucial role of the non-catalytic subunit in tRNA binding. We decipher the functional significance of these additional tRNA-binding sites, analyze solution state conformation, flexibility, and disorder of apo TGT, and examine conformational transitions upon tRNA binding.
真核生物的tRNA鸟嘌呤转糖基酶（TGT）是一种RNA修饰酶，它催化tRNA上遗传编码的鸟嘌呤34与queuine（一种高度修饰的7-脱氮鸟嘌呤衍生物）之间的碱基交换。真核生物TGT是一种异二聚体，由一个催化亚基和一个非催化亚基组成。虽然tRNA反密码子环与活性位点的结合在结构上已得到很好的理解，但非催化亚基对tRNA结合的贡献仍然是个谜，因为没有完整tRNA的复合物结构。在这里，我们报告了真核生物TGT与完整tRNA复合物的冷冻电镜结构，揭示了非催化亚基在tRNA结合中的关键作用。我们解读了这些额外tRNA结合位点的功能意义，分析了无apo TGT的溶液状态构象、灵活性和无序性，并研究了tRNA结合后的构象转变。
