Involvement of CarA/LitR and CRP/FNR Family Transcriptional Regulators in Light-Induced Carotenoid Production in Thermus thermophilus
Involvement of CarA/LitR and CRP/FNR Family Transcriptional Regulators in Light-Induced Carotenoid Production in Thermus thermophilus
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DOI：
10.1128/jb.01125-10
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发表时间：
2011-03
影响因子：
3.2
通讯作者：
H. Takano;M. Kondo;Noriyoshi Usui;T. Usui;Hiromichi Ohzeki;R. Yamazaki;Misato Washioka;A. Nakamura;T. Hoshino;W. Hakamata;T. Beppu;K. Ueda
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文献类型：
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作者：
H. Takano;M. Kondo;Noriyoshi Usui;T. Usui;Hiromichi Ohzeki;R. Yamazaki;Misato Washioka;A. Nakamura;T. Hoshino;W. Hakamata;T. Beppu;K. Ueda
CarA/LitR家族成员是MerR型转录调节因子，其C末端含有钴胺素结合结构域。他们被认为是参与光诱导的转录调控在各种各样的非光养细菌。基于这种调节剂的分布，本研究考察了嗜热栖热菌类胡萝卜素的产生，发现它以光诱导的方式发生。litR、类胡萝卜素和钴胺素生物合成基因均位于该菌的大质粒上。litR或钴胺素生物合成基因敲除突变体不能在黑暗条件下关闭类胡萝卜素的产生，而在与litR相邻的下游基因中具有突变的突变体（TT_P0055）（其编码CRP/FNR家族转录调节因子）不能产生类胡萝卜素，而与光照条件无关。总体而言，遗传和生化证据表明，LitR与钴胺素结合，并与litR和crtB（八氢番茄红素合成酶基因）之间的基因间启动子区域相关，抑制litR和crtB的双向转录。这可能是由某些光依赖机制引起的LitR的去阻遏诱导TT_P0055蛋白的表达，TT_P0055蛋白作为crtB操纵子的转录激活因子，从而引起类胡萝卜素生物合成和DNA修复系统在光条件下的表达。
ABSTRACT Members of the CarA/LitR family are MerR-type transcriptional regulators that contain a C-terminal cobalamin-binding domain. They are thought to be involved in light-induced transcriptional regulation in a wide variety of nonphototrophic bacteria. Based on the distribution of this kind of regulator, the current study examined carotenoid production in Thermus thermophilus, and it was found to occur in a light-induced manner. litR and carotenoid and cobalamin biosynthesis genes were all located on the large plasmid of this organism. litR or cobalamin biosynthesis gene knockout mutants were unable to switch off carotenoid production under dark conditions, while a mutant with a mutation in the downstream gene adjacent to litR (TT_P0055), which encodes a CRP/FNR family transcriptional regulator, was unable to produce carotenoids, irrespective of light conditions. Overall, genetic and biochemical evidence indicates that LitR is bound by cobalamin and associates with the intergenic promoter region between litR and crtB (phytoene synthase gene), repressing the bidirectional transcription of litR and crtB. It is probable that derepression of LitR caused by some photodependent mechanism induces the expression of TT_P0055 protein, which serves as a transcriptional activator for the crtB operon and hence causes the expression of carotenoid biosynthesis and the DNA repair system under light condition.