To date, tripartite tricarboxylate transport (TTT) systems are not well characterized in most organisms. To investigate which carbon sources are transported by the TTT system of A. mimigardefordensis DPN7^T, single deletion mutants were generated lacking either completely both sets of genes encoding for these transport systems tctABCDE1 and tctABDE2 in the organism or the two genes encoding for the regulatory components of the third chosen TTT system, tctDE3. Deletion of tctABCDE1 (MIM_c39170–MIM_c39210) in Advenella mimigardefordensis strain DPN7^T led to inhibition of growth of the cells with citrate indicating that TctABCDE1 is the transport system for the uptake of citrate. Because of the negative phenotype, it was concluded that this deletion cannot be substituted by other transporters encoded in the genome of strain DPN7^T. A triple deletion mutant of A. mimigardefordensis lacking both complete TTT transport systems and the regulatory components of the third chosen system (ΔTctABCDE1 ΔTctABDE2 ΔTctDE3) showed a leaky growth with α-ketoglutarate in comparison with the wild type. The other investigated TTT (TctABDE3, MIM_c17190–MIM_c17220) is most probably involved in the transport of α-ketoglutarate. Additionally, thermoshift assays with TctC1 (MIM_c39190) showed a significant shift in the melting temperature of the protein in the presence of citrate whereas no shift occurred with α-ketoglutarate. A dissociation constant K_d for citrate of 41.7 μM was determined. Furthermore, alternative α-ketoglutarate transport was investigated via in silico analysis.

中文翻译：

---

柠檬阿米德氏菌DPN7T的三羧酸三羧酸盐转运蛋白（MIM_c39170-MIM_c39210）与柠檬酸盐的吸收有关。

迄今为止，在大多数生物中，三羧酸三羧酸盐转运（TTT）系统尚未很好地表征。为了研究米曲霉DPN7 ^T的TTT系统转运了哪些碳源，生成了缺失缺失的突变体，该突变体在生物体中既没有完全编码这两个转运系统tct ABCDE1和tct ABDE2的两个基因，也没有两个基因。第三个选择的TTT系统tct DE3的管理组件。在mimigardefordensis菌株DPN7 ^T中删除tct ABCDE1（MIM_c39170–MIM_c39210）导致柠檬酸盐抑制细胞生长，表明TctABCDE1是摄取柠檬酸盐的转运系统。由于具有负表型，因此得出结论，该缺失不能被菌株DPN7 ^T的基因组中编码的其他转运蛋白取代。米氏拟南芥的三重缺失突变体缺乏完整的TTT转运系统和第三个选择的系统（ΔTctABCDE1ΔTctABDE2ΔTctDE3）的调节成分，与野生型相比，α-酮戊二酸的生长出现泄漏。其他研究的TTT（TctABDE3，MIM_c17190–MIM_c17220）最可能与α-酮戊二酸的转运有关。此外，使用TctC1（MIM_c39190）进行的热位移分析表明，在柠檬酸盐存在的情况下，蛋白质的解链温度发生了显着变化，而α-酮戊二酸则没有发生变化。测定的柠檬酸盐的解离常数K _d为41.7μM。此外，通过计算机分析研究了替代的α-酮戊二酸转运。