Role for the outer membrane ferric siderophore receptor PupB in signal transduction across the bacterial cell envelope.

Abstract

The outer membrane protein PupB of Pseudomonas putida WCS358 facilitates transport of iron complexed to the siderophores pseudobactin BN8 and pseudobactin BN7 into the cell. Its synthesis is induced by the presence of these specific siderophores under iron limitation. The signal transduction pathway regulating siderophore‐dependent expression of pupB was shown to consist of two regulatory proteins, PupI and PupR, and the PupB receptor itself. Mutational analysis of the regulatory genes suggested that PupI acts as a positive regulator of pupB transcription, whereas PupR modifies PupI activity dependent on the presence of pseudobactin BN8. PupI and PupR do not share homology with the classical bacterial two‐component systems but display significant similarity to the FecI and FecR proteins of Escherichia coli involved in regulation of ferric dicitrate transport. The function of the PupB receptor in pupB regulation was studied by the use of chimeric receptor proteins composed of PupB and the ferric pseudobactin 358 receptor PupA. This experiment revealed that PupB is involved in the initiation of the signal transduction pathway, implying a so far unique role for an outer membrane protein in signal transduction.

Transcription induction of the ferric citrate transport genes via the N‐terminus of the FecA outer membrane protein, the Ton system and the electrochemical potential of the cytoplasmic membrane

“…The failure to obtain an induction-active FecA-RumA hybrid is in contrast to the PupB-PupA hybrid, through which synthesis of PupB, the receptor for pseudobactins BN7 and BN8, could be induced by binding of pseudobactin 358 to PupA (Koster et al, 1994). Presumably, the two receptors of Pseudomonas putida are similar enough to form an active hybrid; this is not the case with the rather different receptors from two different species, FecA and RumA, which recognize rather different substrates.…”

Heme Utilization in Bordetella avium Is Regulated by RhuI, a Heme-Responsive Extracytoplasmic Function Sigma Factor

“…Recently, a new family of Fe-responsive regulatory proteins which have characteristics of sigma factors and that respond indirectly to Fe was identified (21,22,37,43). Sigma factors are small polypeptides which provide transcriptional specificity to RNA polymerase for promoter sequences (47).…”

“…Sigma factors are small polypeptides which provide transcriptional specificity to RNA polymerase for promoter sequences (47). In contrast to other sigma factors, this new class of Fe-responsive sigma factors requires extracellular molecules to induce their biological activities (21,22,37,43). To differentiate these inducible transcriptional regulators from other alternative sigma factors, these sigma factors have been designated extracytoplasmic function (ECF) sigma factors.…”

Identification of differentially expressed genes of Xanthomonas axonopodis pv. citri by representational difference analysis of cDNA

“…Fe is the limiting factor of bacterial growth in planta since micromolar concentrations of iron are necessary to permit bacterial growth and multiplication. The TonB system also mediates the signal transduction from the cellular surface to the cytoplasm, as reported in E. coli and Pseudomonas putida (Harle et al, 1995;Koster et al, 1994). In X. campestris, the genes involved in the uptake of Fe are essential for the induction of a hypersensitive response (Wiggerich and Puhler, 2000).…”