Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, iRTSV, CEA, Grenoble, France.
BMC Microbiol. 2010 Oct 28;10:271. doi: 10.1186/1471-2180-10-271.
Ferredoxins are small iron-sulfur proteins belonging to all domains of life. A sub-group binds two [4Fe-4S] clusters with unequal and extremely low values of the reduction potentials. These unusual properties are associated with two specific fragments of sequence. The functional importance of the very low potential ferredoxins is unknown.
A bioinformatic screening of the sequence features defining very low potential 2[4Fe-4S] ferredoxins has revealed the almost exclusive presence of the corresponding fdx gene in the Proteobacteria phylum, without occurrence in Archaea and Eukaryota. The transcript was found to be monocistronic in Pseudomonas aeruginosa, and not part of an operon in most bacteria. Only fdx genes of bacteria which anaerobically degrade aromatic compounds belong to operons. As this pathway is not present in all bacteria having very low potential 2[4Fe-4S] ferredoxins, these proteins cannot exclusively be reductants of benzoyl CoA reductases. Expression of the ferredoxin gene did not change in response to varying growth conditions, including upon macrophage infection or aerobic growth with 4-hydroxy benzoate as carbon source. However, it increased along the growth curve in Pseudomonas aeruginosa and in Escherichia coli. The sequence immediately 5' upstream of the coding sequence contributed to the promotor activity. Deleting the fdx gene in Pseudomonas aeruginosa abolished growth, unless a plasmid copy of the gene was provided to the deleted strain.
The gene of the very low potential 2[4Fe-4S] ferredoxin displays characteristics of a housekeeping gene, and it belongs to the minority of genes that are essential in Pseudomonas aeruginosa. These data identify a new potential antimicrobial target in this and other pathogenic Proteobacteria.
铁氧还蛋白是一种小型铁硫蛋白，存在于所有生命领域。一个亚群结合两个[4Fe-4S]簇，其还原电势值极低且极不相等。这些不寻常的特性与两个特定的序列片段有关。非常低潜力铁氧还蛋白的功能重要性尚不清楚。
对定义非常低潜力 2[4Fe-4S]铁氧还蛋白的序列特征进行生物信息学筛选，发现几乎只在变形菌门中存在相应的fdx 基因，而在古菌和真核生物中不存在。在铜绿假单胞菌中发现该转录物为单顺反子，而在大多数细菌中不是操纵子的一部分。只有在无氧降解芳香族化合物的细菌中，fdx 基因才属于操纵子。由于该途径不存在于所有具有非常低潜力 2[4Fe-4S]铁氧还蛋白的细菌中，因此这些蛋白不能仅仅作为苯甲酰辅酶 A 还原酶的还原剂。铁氧还蛋白基因的表达不会随生长条件的变化而变化，包括在巨噬细胞感染或有氧生长时以 4-羟基苯甲酸为碳源。然而，在铜绿假单胞菌和大肠杆菌中，随着生长曲线的增加，其表达量增加。编码序列上游的 5'序列有助于启动子活性。在铜绿假单胞菌中删除 fdx 基因会导致生长停止，除非为缺失菌株提供质粒拷贝的基因。
非常低潜力 2[4Fe-4S]铁氧还蛋白的基因显示出管家基因的特征，它属于铜绿假单胞菌中必需基因的少数。这些数据确定了该基因和其他致病变形菌中的一个新的潜在抗菌靶标。
