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Study on Iron Regulon Pseudomonas aeruginosa

铜绿假单胞菌铁调节的研究

基本信息

批准号：
05670258
负责人：
TSUDA Masataka
金额：
$ 1.34万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

Under iron limitation, Pseudomonas aeruginosa secretes pyoverdin, a low-molecular-weight siderophore able to capture ferric iron with a very high affinity for uptake of this ion into the cell. A number of pvd genes involved in pyoverdin production were found to be clustered and organized in many operons at the 47 min region (pvd region) on the chromosomal genetic map. Genetic analysis of the three pvd operons demonstrated that their transcription (1) was repressed under iron-rich conditions and (2) required a positive regulator, PvdS,that was encoded in the pvd region. Based on uncleotide sequencing and subsequent homology search, it was inferred that PvdS is a member of subfamily of RNA polymerase sigma factors regulating "extracytoplasmic functions" . The promoter region of pvdS contained the sequence that matched well with the consensus binding sequence of Fur, a global repressor of the iron regulon. Consistent with the presence of such a sequence (Fur box) , transcription of pvdS was repressed under iron-rich conditions. The data obtained in this study leads to the proposal that (i) an active form of Fur under an iron-rich condition binds to the Fur box at the pvdS promoter to repress the transcription of pvdS and (ii) no production of PvdS thereafter does not permit the transcription of other structural pvd genes. Because of the most probable involvement of Fur in pyoverdin production, allelic exchange mutagenesis was carried out to isolate a chromosomal fur mutation. Our repeated attempt to obtain such a mutation was unsuccessful, suggesting the essential role of Fur on the viability of P.aeruginosa.

在铁限制下，铜绿假单胞菌分泌绿脓菌荧光素，这是一种低分子量的铁载体，能够以非常高的亲和力捕获三价铁，将该离子吸收到细胞中。发现许多参与绿脓菌荧光素产生的pvd基因在染色体遗传图谱上的47 min区域（pvd区域）聚集并组织在许多操纵子中。三个pvd操纵子的遗传分析表明，它们的转录（1）在富铁条件下受到抑制，（2）需要一个编码在pvd区域的正调节因子PvdS。基于核苷酸测序和随后的同源性搜索，推测PvdS是调节“细胞质外功能”的RNA聚合酶σ因子亚家族的成员。pvdS的启动子区域包含与铁调节子的全局阻遏物Fur的共有结合序列匹配良好的序列。与存在这样的序列（毛皮盒），pvdS的转录被阻遏在富铁条件下。本研究中获得的数据导致以下建议：（i）在富铁条件下，活性形式的Fur与pvdS启动子处的Fur盒结合，以抑制pvdS的转录，以及（ii）此后不产生PvdS，不允许其他结构性pvd基因的转录。由于Fur最有可能参与绿脓菌荧光素生产，因此进行等位基因交换诱变以分离染色体Fur突变。我们多次尝试获得这样的突变是不成功的，这表明毛皮的重要作用的P.aerodosa.的生存能力。