Koster M, van de Vossenberg J, Leong J, Weisbeek P J
Department of Molecular Cell Biology, University of Utrecht, Netherlands.
Mol Microbiol. 1993 May;8(3):591-601. doi: 10.1111/j.1365-2958.1993.tb01603.x.
Pseudomonas putida WCS358 can transport iron complexed to a wide variety of pseudobactins produced by other Pseudomonas strains. The pupB gene encoding an outer membrane ferric-pseudobactin receptor was isolated from a genomic library of P. putida WCS358. The PupB receptor facilitated iron transport via two distinct heterologous siderophores, i.e. pseudobactin BN8 and pseudobactin BN7. The amino acid sequence deduced from the nucleotide sequence consisted of 804 amino acids (molecular weight 88,369) of which the N-terminal part was very similar to a prokaryotic leader peptide. The mature protein shared significant homology with the receptor for ferric-pseudobactin 358 (PupA) and contained three regions common to TonB-dependent receptor proteins of Escherichia coli. Interestingly, PupB expression was only observed in cells cultured in iron-deficient medium containing pseudobactin BN8 or pseudobactin BN7. This expression required a transcriptional unit, pupR, identified upstream of the structural pupB gene. Transposon Tn5 insertion mutants defective in PupB production still exhibited uptake of iron via pseudobactin BN8, although with reduced efficiency. Apparently, an additional transport system for this ferric-siderophore complex operates in this strain. In addition to pseudobactin BN8 also other heterologous siderophores were capable of inducing synthesis of specific high-molecular-weight outer membrane proteins in strain WCS358, which suggests the existence of multiple siderophore-inducible iron transport systems in this strain.
恶臭假单胞菌WCS358能够转运与其他假单胞菌菌株产生的多种假单胞菌素络合的铁。从恶臭假单胞菌WCS358的基因组文库中分离出编码外膜铁 - 假单胞菌素受体的pupB基因。PupB受体通过两种不同的异源铁载体促进铁的转运，即假单胞菌素BN8和假单胞菌素BN7。从核苷酸序列推导的氨基酸序列由804个氨基酸组成（分子量88,369），其中N端部分与原核前导肽非常相似。成熟蛋白与铁 - 假单胞菌素358受体（PupA）具有显著同源性，并包含大肠杆菌TonB依赖性受体蛋白共有的三个区域。有趣的是，仅在含有假单胞菌素BN8或假单胞菌素BN7的缺铁培养基中培养的细胞中观察到PupB表达。这种表达需要在结构pupB基因上游鉴定的转录单元pupR。在PupB产生中存在缺陷的转座子Tn5插入突变体仍然通过假单胞菌素BN8表现出铁的摄取，尽管效率降低。显然，该菌株中存在另一种用于这种铁 - 铁载体复合物的转运系统。除了假单胞菌素BN8之外，其他异源铁载体也能够在菌株WCS358中诱导合成特定的高分子量外膜蛋白，这表明该菌株中存在多种铁载体诱导的铁转运系统。
