Identification and characterization of the pupB gene encoding an inducible ferric-pseudobactin receptor of Pseudomonas putida WCS358.
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.
Department of Molecular Cell Biology, University of Utrecht, Netherlands.
M
M
Koster
J
J
van de Vossenberg
J
J
Leong
P J
PJ
Weisbeek
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D005798:Genes, Bacterial; D007501:Iron / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009842:Oligopeptides / Q000378:metabolism*; D021382:Protein Sorting Signals / Q000235:genetics; D016958:Pseudomonas putida / Q000187:drug effects / Q000235:genetics*; D011956:Receptors, Cell Surface / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D009842:Oligopeptides; D021382:Protein Sorting Signals; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; C047631:pseudobactin receptor, Pseudomonas; C033038:pseudobactin; D007501:Iron