Unit of Architecture and Dynamics of Biological Macromolecules, CNRS UMR 3528, 25-28 rue du Docteur Roux, Institut Pasteur, Paris, France.
Sorbonne Université, Collège Doctoral, ED 515, Paris, France.
Nat Commun. 2021 Aug 5;12(1):4710. doi: 10.1038/s41467-021-25064-x.
Cyanophage S-2L is known to profoundly alter the biophysical properties of its DNA by replacing all adenines (A) with 2-aminoadenines (Z), which still pair with thymines but with a triple hydrogen bond. It was recently demonstrated that a homologue of adenylosuccinate synthetase (PurZ) and a dATP triphosphohydrolase (DatZ) are two important pieces of the metabolism of 2-aminoadenine, participating in the synthesis of ZTGC-DNA. Here, we determine that S-2L PurZ can use either dATP or ATP as a source of energy, thereby also depleting the pool of nucleotides in dATP. Furthermore, we identify a conserved gene (mazZ) located between purZ and datZ genes in S-2L and related phage genomes. We show that it encodes a (d)GTP-specific diphosphohydrolase, thereby providing the substrate of PurZ in the 2-aminoadenine synthesis pathway. High-resolution crystal structures of S-2L PurZ and MazZ with their respective substrates provide a rationale for their specificities. The Z-cluster made of these three genes - datZ, mazZ and purZ - was expressed in E. coli, resulting in a successful incorporation of 2-aminoadenine in the bacterial chromosomal and plasmidic DNA. This work opens the possibility to study synthetic organisms containing ZTGC-DNA.
噬藻体 S-2L 通过将所有腺嘌呤（A）替换为 2-氨基腺嘌呤（Z），从而深刻改变其 DNA 的生物物理性质，Z 仍然与胸腺嘧啶配对，但具有三氢键。最近的研究表明，腺嘌呤核苷酸合成酶（PurZ）和 dATP 三磷酸水解酶（DatZ）的同源物是 2-氨基腺嘌呤代谢的两个重要部分，参与 ZTGC-DNA 的合成。在这里，我们确定 S-2L PurZ 可以使用 dATP 或 ATP 作为能量来源，从而耗尽 dATP 核苷酸池。此外，我们在 S-2L 和相关噬菌体基因组中鉴定出位于 purZ 和 datZ 基因之间的保守基因（mazZ）。我们表明它编码一种 (d)GTP 特异性二磷酸水解酶，从而为 PurZ 在 2-氨基腺嘌呤合成途径中的提供底物。S-2L PurZ 和 MazZ 及其各自底物的高分辨率晶体结构为它们的特异性提供了依据。由这三个基因（datZ、mazZ 和 purZ）组成的 Z 簇在大肠杆菌中表达，导致细菌染色体和质粒 DNA 成功掺入 2-氨基腺嘌呤。这项工作为研究含有 ZTGC-DNA 的合成生物体开辟了可能性。
