Open AccessZnu Is the Predominant Zinc Importer in Yersinia pestis during In Vitro Growth but Is Not Essential for Virulence
Author(s) -
Daniel C. Desrosiers,
Scott W. Bearden,
Ildefonso Mier,
Jennifer Abney,
James T. Paulley,
Jacqueline D. Fetherston,
Juan C. Salazar,
Justin D. Radolf,
Robert D. Perry
Publication year - 2010
Publication title -
infection and immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.508
H-Index - 220
eISSN - 1070-6313
pISSN - 0019-9567
DOI - 10.1128/iai.00732-10
Subject(s) - yersinia pestis , virulence , biology , isothermal titration calorimetry , zinc , mutant , transporter , in vitro , microbiology and biotechnology , biochemistry , gene , chemistry , organic chemistry
Little is known about Zn homeostasis inYersinia 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 inY. pestis . Mutation ofznuACB 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 theznuACB mutant. Previous studies of cluster 9 (C9) transporters suggested that Yfe, a well-characterized C9 importer for manganese (Mn) and iron inY. 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 inin vitro growth studies. Unexpectedly, overexpression of Yfe interfered with theznu 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 inY. 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 underin 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.