Identification of amino acid residues required for ferric-anguibactin transport in the outer-membrane receptor FatA of Vibrio anguillarum.
Identification of amino acid residues required for ferric-anguibactin transport in the outer-membrane receptor FatA of Vibrio anguillarum.
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DOI：
10.1099/mic.0.2006/001735-0
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发表时间：
2007-02
期刊：
影响因子：
1.5
通讯作者：
C. López;Alejandro F. Alice;R. Chakraborty;J. H. Crosa
中科院分区：
文献类型：
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作者：
C. López;Alejandro F. Alice;R. Chakraborty;J. H. Crosa
鳗弧菌775是一种鱼类病原体，可引起致命的出血性败血症。它含有65kbp的pJM1质粒，编码铁载体angibactin特有的铁隔离系统，对毒力是必不可少的。参与angibactin生物合成的基因位于pJM1质粒和染色体上。然而，外膜受体FATA和其他运输蛋白的基因只在质粒上携带。为了阐明FATA介导的铁-愈创木蛋白转运的机制，本工作通过分析定点突变体的转运动力学，鉴定了在铁-愈创木蛋白转运过程中起作用的FATA氨基酸残基。所研究的突变位于锁定区和FATA通道区的保守残基中，锁定区包含属于N-末端和桶结构域的10个残基，通道区包含位于Beta5-Beta6环的保守甘氨酸和位于Beta5-桶11链的保守精氨酸。以FATA锁定区为例，很明显，尽管本工作中分析的残基(R95、K130、E505和E550)在各种外膜受体中是保守的，但它们在转运过程中的参与可能因受体而异。此外，在FATA通道区，保守的甘氨酸131和143与丙氨酸的双重取代导致了一个不同的受体不能运输铁-钩肌动蛋白。研究还表明，位于链11上的保守的精氨酸428是运输所必需的。结果表明，在铁-angibactin转运过程中，Plug结构域发生了构象变化或部分展开。
Vibrio anguillarum 775 is a fish pathogen that causes a disease characterized by a fatal haemorrhagic septicaemia. It harbours the 65 kbp pJM1 plasmid, which encodes an iron sequestering system specific for the siderophore anguibactin and is essential for virulence. The genes involved in the biosynthesis of anguibactin are located on both the pJM1 plasmid and the chromosome. However, the genes for the outer-membrane receptor FatA and the other transport proteins are only carried on the plasmid. With the aim of elucidating the mechanism of ferric-anguibactin transport mediated by FatA, this work focuses on the identification of FatA amino acid residues that play a role in the transport of ferric-anguibactin, by analysing the transport kinetics of site-directed mutants. The mutations studied were located in conserved residues of the lock region, which contains a cluster of ten residues belonging to the N-terminal and barrel domains, and of the channel region of FatA, which contains conserved glycines located in the beta5-beta6 loop and a conserved arginine located in strand 11 of the beta-barrel. In the case of the FatA lock region, it is clear that although the residues analysed in this work (R95, K130, E505 and E550) are conserved among various outer-membrane receptors, their involvement in the transport process might differ among receptors. Furthermore, it was determined that in the FatA channel region double substitutions of the conserved glycines 131 and 143 with alanine resulted in a variant receptor unable to transport ferric-anguibactin. It was also shown that the conserved arginine 428 located in strand 11 is essential for transport. The results suggest that a conformational change or partial unfolding of the plug domain occurs during ferric-anguibactin transport.