Last data update: May 13, 2024. (Total: 46773 publications since 2009)
Records 1-2 (of 2 Records) |
Query Trace: Paulley JT[original query] |
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The iron-responsive regulator irr is required for wild-type expression of the gene encoding the heme transporter BhuA in Brucella abortus 2308.
Anderson ES , Paulley JT , Martinson DA , Gaines JM , Steele KH , Roop RM 2nd . J Bacteriol 2011 193 (19) 5359-64 Irr and RirA, rather than Fur, serve as the major iron-responsive regulators in the alphaproteobacteria. With only a few exceptions, however, the relative contributions of these transcriptional regulators to the differential expression of specific iron metabolism genes in Brucella strains are unclear. The gene encoding the outer membrane heme transporter BhuA exhibits maximum expression in Brucella abortus 2308 during growth under iron-deprived conditions, and mutational studies indicate that this pattern of bhuA expression is mediated by the iron-responsive regulator Irr. Specifically, a bhuA-lacZ transcriptional fusion does not produce elevated levels of beta-galactosidase in response to iron deprivation in the isogenic irr mutant BEA5, and, unlike the parental strain, B. abortus BEA5 cannot utilize heme as an iron source in vitro and is attenuated in mice. A derivative of the bhuA-lacZ transcriptional fusion lacking the predicted Irr binding site upstream of the bhuA promoter does not produce elevated levels of beta-galactosidase in response to iron deprivation in the parental B. abortus 2308 strain, and a direct and specific interaction between a recombinant version of the Brucella Irr and the bhuA promoter region was observed in an electrophoretic mobility shift assay. Despite the fact that it lacks the heme regulatory element linked to the iron-responsive degradation of its counterpart in Bradyrhizobium japonicum, readily detectable levels of Irr were found only in B. abortus 2308 cells by Western blot analysis following growth under iron-deprived conditions. |
Znu is the predominant zinc importer in Yersinia pestis during in vitro growth but is not essential for virulence
Desrosiers DC , Bearden SW , Mier I Jr , Abney J , Paulley JT , Fetherston JD , Salazar JC , Radolf JD , Perry RD . Infect Immun 2010 78 (12) 5163-77 Little is known about Zn homeostasis in Yersinia pestis, the plague bacillus. The Znu ABC transporter is essential for zinc (Zn) uptake and virulence in a number of bacterial pathogens. Bioinformatics analysis identified ZnuABC as the only apparent high-affinity Zn uptake system in Y. pestis. Mutation of znuACB caused a growth defect in Chelex-100-treated PMH2 growth medium, which was alleviated by supplementation with submicromolar concentrations of Zn. Use of transcriptional reporters confirmed that Zur mediated Zn-dependent repression and that it can repress gene expression in response to Zn even in the absence of Znu. Virulence testing in mouse models of bubonic and pneumonic plague found only a modest increase in survival in low-dose infections by the znuACB mutant. Previous studies of cluster 9 (C9) transporters suggested that Yfe, a well-characterized C9 importer for manganese (Mn) and iron in Y. pestis, might function as a second, high-affinity Zn uptake system. Isothermal titration calorimetry revealed that YfeA, the solute-binding protein component of Yfe, binds Mn and Zn with comparably high affinities (dissociation constants of 17.8 +/- 4.4 nM and 6.6 +/- 1.2 nM, respectively), although the complete Yfe transporter could not compensate for the loss of Znu in in vitro growth studies. Unexpectedly, overexpression of Yfe interfered with the znu mutant's ability to grow in low concentrations of Zn, while excess Zn interfered with the ability of Yfe to import iron at low concentrations; these results suggest that YfeA can bind Zn in the bacterial cell but that Yfe is incompetent for transport of the metal. In addition to Yfe, we have now eliminated MntH, FetMP, Efe, Feo, a substrate-binding protein, and a putative nickel transporter as the unidentified, secondary Zn transporter in Y. pestis. Unlike other bacterial pathogens, Y. pestis does not require Znu for high-level infectivity and virulence; instead, it appears to possess a novel class of transporter, which can satisfy the bacterium's Zn requirements under in vivo metal-limiting conditions. Our studies also underscore the need for bacterial cells to balance binding and transporter specificities within the periplasm in order to maintain transition metal homeostasis. |
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