Genetics and regulation of two distinct haem-uptake systems, phu and has, in Pseudomonas aeruginosa
Genetics and regulation of two distinct haem-uptake systems, phu and has, in Pseudomonas aeruginosa
复制标题
DOI：
10.1099/00221287-146-1-185
复制
发表时间：
2000-01-01
期刊：
影响因子：
--
通讯作者：
Vasil, ML
中科院分区：
文献类型：
--
作者：
Ochsner, UA;Johnson, Z;Vasil, ML
在铜绿假单胞菌中发现了一个类似细菌病原体血红素铁摄取位点的基因簇。这个phu位点（“假单胞菌血红素吸收”）由phuR受体基因和编码典型ABC转运蛋白的phuSTOVW操纵子组成，phuR和phuSTOVW在转录起始位点的表达发生在铁限制生长条件下，并由Fur蛋白直接控制。通过DNase标记两个相邻的“Fur box”来证明Fur的结合，这两个“Fur box”重叠了phuR和phuSTUVW启动子。在phuSTUVW操纵子下游鉴定了两个154 bp的串联重复序列，每个重复序列都含有一个强的fur依赖启动子，驱动铁调控rna对phuSTUVW的反义表达。phuR和phuSTUV缺失的突变株在血红素或血红蛋白作为唯一铁源的情况下，生长显著降低：缺陷分别由含有phuR或phuSTUV基因的质粒补充。phuW或串联重复序列的缺失对血红素利用的影响很小。在Delta phuR或Delta phuSTUV缺失突变体中仍然观察到剩余的血红素和血红蛋白摄取，这是由于第二个血液获取系统，也在Fur的直接控制下。第二种血液受体基因hasR被鉴定为位于具有hasA的操纵子上游，编码一种与血液结合的细胞外蛋白。Delta hasR突变体对血红素和血红蛋白的利用也下降，而Delta phuR Delta hasR双突变体实际上无法吸收这两种化合物。在低铁培养基中培养的铜绿假单胞菌外膜部分均检测到PhuR和HasR蛋白。综上所述，证据表明phu和has基因座编码了铜绿假单胞菌获得血红素和血红蛋白所需的两个不同系统。
A gene cluster similar to haem iron uptake loci of bacterial pathogens was identified in Pseudomonas aeruginosa. This phu locus ('Pseudomonas haem uptake') consisted of the phuR receptor gene and the phuSTOVW operon encoding a typical ABC transporter Expression of phuR and phuSTUVW from mapped transcriptional-start sites occurred under iron-restricted growth conditions and was directly controlled by the Fur protein. Binding of Fur was demonstrated by DNase footprinting of two adjacent 'Fur boxes' that: overlapped both the phuR and phuSTUVW promoters. Two tandem repeats of 154 bp were identified downstream of the phuSTUVW operon, each of which contained a strong Fur-dependent promoter driving expression of iron-regulated RNAs antisense to phuSTUVW. Mutant strains with deletions in phuR and phuSTUV showed greatly reduced growth with either haem or haemoglobin as the only iron source: the defects were complemented by plasmids harbouring the phuR or the phuSTUV genes, respectively. Deletions of phuW or of the tandem repeats had only minor effects on haem utilization. The remaining haem and haemoglobin uptake still observed in the Delta phuR or Delta phuSTUV deletion mutants was due to a second haem-acquisition system, has, which was also under the direct control of Fur. This second haem-receptor gene, hasR, was identified upstream of and in an operon with hasA, encoding a haem-binding extracellular protein. A Delta hasR mutant also exhibited decreased utilization of haem and haemoglobin, and a Delta phuR Delta hasR double mutant was virtually unable to take up either compound. Both the PhuR and HasR proteins were detected in the outer-membrane fraction of P. aeruginosa grown in low-iron media. Taken together, the evidence suggests that the phu and has loci encode two distinct systems required for the acquisition of haem and haemoglobin in P. aeruginosa.