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首页> 外文期刊>Journal of bacteriology >Chlamydia trachomatis Transports NAD via the Npt1 ATP/ADP Translocase
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Chlamydia trachomatis Transports NAD via the Npt1 ATP/ADP Translocase

机译：沙眼衣原体通过Npt1 ATP / ADP转运酶转运NAD

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Obligate intracellular bacteria comprising the order Chlamydiales lack the ability to synthesize nucleotides de novo and must acquire these essential compounds from the cytosol of the host cell. The environmental protozoan endosymbiont Protochlamydia amoebophila UWE25 encodes five nucleotide transporters with specificities for different nucleotide substrates, including ATP, GTP, CTP, UTP, and NAD. In contrast, the human pathogen Chlamydia trachomatis encodes only two nucleotide transporters, the ATP/ADP translocase C. trachomatis Npt1 (Npt1Ct) and the nucleotide uniporter Npt2Ct, which transports GTP, UTP, CTP, and ATP. The notable absence of a NAD transporter, coupled with the lack of alternative nucleotide transporters on the basis of bioinformatic analysis of multiple C. trachomatis genomes, led us to re-evaluate the previously characterized transport properties of Npt1Ct. Using [adenylate-32P]NAD, we demonstrate that Npt1Ct expressed in Escherichia coli enables the transport of NAD with an apparent Km and Vmax of 1.7 μM and 5.8 nM mg?1 h?1, respectively. The Km for NAD transport is comparable to the Km for ATP transport of 2.2 μM, as evaluated in this study. Efflux and substrate competition assays demonstrate that NAD is a preferred substrate of Npt1Ct compared to ATP. These results suggest that during reductive evolution, the pathogenic chlamydiae lost individual nucleotide transporters, in contrast to their environmental endosymbiont relatives, without compromising their ability to obtain nucleotides from the host cytosol through relaxation of transport specificity. The novel properties of Npt1Ct and its conservation in chlamydiae make it a potential target for the development of antimicrobial compounds and a model for studying the evolution of transport specificity.
机译：包含衣原体命令的专性细胞内细菌缺乏合成核苷酸 de novo 的能力，并且必须从宿主细胞的细胞质中获得这些必需的化合物。环境原生动物内共生菌原虫嗜血杆菌UWE25编码五个核苷酸转运蛋白，对不同的核苷酸底物具有特异性，包括ATP，GTP，CTP，UTP和NAD。相比之下，人类病原体沙眼衣原体仅编码两个核苷酸转运蛋白，即ATP / ADP转运沙眼衣原体Npt1（Npt1 Ct ）和核苷酸单转运蛋白Npt2 Ct 。 GTP，UTP，CTP和ATP。 NAD转运蛋白的显着缺失，再加上根据多个沙眼衣原体基因组的生物信息学分析，缺乏替代核苷酸转运蛋白，导致我们重新评估了Npt1 Ct 以前表征的转运特性。使用[腺苷酸- 32 P] NAD，我们证明了在大肠杆菌中表达的Npt1 Ct 能够以明显的 K m 转运NAD。 sub> 和 V max 分别为1.7μM和5.8 nM mg ？1 h ？1 ，分别。 NAD转运的 K m 与ATP转运的 K m 相当，如2.2μM。这项研究。流出和底物竞争测定表明，与ATP相比，NAD是Npt1 Ct 的优选底物。这些结果表明，在还原性进化过程中，与环境内共生体亲戚相比，病原体衣原体丢失了单个核苷酸转运蛋白，而不损害其通过放松转运特异性从宿主细胞质中获得核苷酸的能力。 Npt1 Ct 的新颖性质及其在衣原体中的保守性使其成为开发抗菌化合物的潜在目标和研究转运特异性进化的模型。

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