Abstract

Agrobacterium tumefaciens synthesizes polyphosphate (polyP) in the form of one or two polyP granules per cell during growth. The A. tumefaciens genome codes for two polyphosphate kinase genes, ppk1_AT and ppk2_AT, of which only ppk1_AT is essential for polyP granule formation in vivo. Biochemical characterization of the purified PPK1_AT and PPK2_AT proteins revealed a higher substrate specificity of PPK1_AT (in particular for adenine nucleotides) than for PPK2_AT. In contrast, PPK2_AT accepted all nucleotides at comparable rates. Most interestingly, PPK2_AT catalyzed also the formation of tetra-, penta-, hexa-, hepta-, and octa-phosphorylated nucleosides from guanine, cytosine, desoxy-thymidine, and uridine nucleotides and even nona-phosphorylated adenosine. Our data—in combination with in vivo results—suggest that PPK1_AT is important for the formation of polyP whereas PPK2_AT has the function to replenish nucleoside triphosphate pools during times of enhanced demand. The potential physiological function(s) of the detected oligophosphorylated nucleotides await clarification.

Key points

•PPK1_AT and PPK2_AT have different substrate specificities,

•PPK2 _AT is a subgroup 1 member of PPK2s,

•PPK2 _AT catalyzes the formation of polyphosphorylated nucleosides

中文翻译：

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根癌农杆菌PPKs的表征揭示了寡磷酸化产物的形成，直至核苷九磷酸

摘要

根癌土壤杆菌在生长过程中每个细胞以一个或两个polyP颗粒的形式合成多磷酸盐（polyP）。的根瘤农杆菌基因组编码两个多磷酸激酶基因，ppk1 _AT和ppk2 _AT，其中只有ppk1 _AT是用于体内息肉颗粒形成是必不可少的。纯化PPK1的生物化学表征_AT和PPK2 _AT蛋白质揭示PPK1更高的底物特异性_AT（腺嘌呤核苷酸尤其是）比PPK2 _AT。相反，PPK2 _AT以可比的速率接受所有核苷酸。最有趣的是，PPK2_AT还催化了鸟嘌呤，胞嘧啶，脱氧胸苷和尿苷核苷酸，甚至九磷酸腺苷形成的四，五，六，七和八磷酸核苷。我们的数据与体内结果相结合，表明PPK1 _AT对polyP的形成很重要，而PPK2 _AT具有在需求增加时补充三磷酸核苷池的功能。检测到的寡磷酸化核苷酸的潜在生理功能在等待澄清。

关键点

• PPK1 _AT 和PPK2 _AT 具有不同的底物特异性，

•PPK2 _AT是PPK2的第1组子成员，

•PPK2 _AT催化多磷酸化核苷的形成