Miyazaki H, Kato H, Nakazawa T, Tsuda M
Department of Gynecology and Obstetrics, Yamaguchi University School of Medicine, Ube, Japan.
Mol Gen Genet. 1995 Jul 22;248(1):17-24. doi: 10.1007/BF02456609.
In response to iron limitation Pseudomonas aeruginosa PAO induces production of pyoverdin, a low-molecular-weight siderophore able to capture ferric ion with a very high affinity. The pvd genes involved in the pyoverdin biosynthesis are organized in a chromosomal region termed the pvd region, and expression of some pvd genes is regulated at the transcriptional level. Two sets of promoter regions for the pvd genes were defined that were transcriptionally derepressed under iron-limiting conditions. Analysis of transcription from such promoters in Escherichia coli led to isolation and identification of a positive regulatory gene, pvdS, for expression of the pvd genes, and pvdS was localized in the pvd region. A genomic pvdS mutant of PAO, constructed by allelic exchange mutagenesis, produced no pyoverdin and did not allow transcription from the pvd promoters. Nucleotide sequence analysis revealed that PvdS shows considerable similarity to FecI of E. coli, a positive regulator for transcription of the fec (ferric citrate transport system) operon. The promoter region of pvdS has the sequence that matches well the consensus binding site for the E. coli Fur protein, a global negative regulatory protein that represses the transcription of the iron-repressible genes. Consistent with the presence of such a consensus sequence, addition of iron repressed transcription of the pvdS gene in P. aeruginosa.
为应对铁限制，铜绿假单胞菌PAO诱导产生绿脓菌素，这是一种低分子量的铁载体，能够以非常高的亲和力捕获铁离子。参与绿脓菌素生物合成的pvd基因在一个称为pvd区域的染色体区域中组织，并且一些pvd基因的表达在转录水平上受到调控。定义了两组pvd基因的启动子区域，它们在铁限制条件下转录去抑制。在大肠杆菌中对此类启动子的转录分析导致分离和鉴定了一个用于pvd基因表达的正调控基因pvdS，并且pvdS定位于pvd区域。通过等位基因交换诱变构建的PAO基因组pvdS突变体不产生绿脓菌素，并且不允许从pvd启动子进行转录。核苷酸序列分析表明，PvdS与大肠杆菌的FecI有相当大的相似性，FecI是柠檬酸铁转运系统（fec）操纵子转录的正调控因子。pvdS的启动子区域具有与大肠杆菌Fur蛋白的共有结合位点匹配良好的序列，Fur蛋白是一种全局负调控蛋白，可抑制铁可抑制基因的转录。与这种共有序列的存在一致，添加铁会抑制铜绿假单胞菌中pvdS基因的转录。
