SummaryIn Streptococcus pyogenes, mutation of the peroxide sensor PerR results in avirulence despite producing hyper-resistance to peroxide stress. To understand the basis of this effect, global transcription profiling was conducted revealing one highly downregulated gene (czcD), and five highly upregulated genes in the mutant. Of the latter, only pmtA contained a binding site for PerR, while phtY, phtD, lsp and rpsN2 harboured an AdcR motif and were regulated by AdcR, a repressor of an ABC-type metal transporter. Furthermore, only the PerR-regulated pmtA (PerR-regulated metal transporter A), a putative metal transporter, contributed to resistance against peroxide stress, while AdcR and the other AdcR-regulated genes did not. However, overexpression of pmtA resulted in upregulation of several AdcR-regulated genes, suggesting that the AdcR regulon is sensitive to PerR regulation of metal homeostasis. Finally, examination of S. pyogenes following murine subcutaneous infection revealed that while pmtA was not upregulated in a late infection, the AdcR-regulated genes were. Taken together, these data suggest that PerR has a greater impact on the transcriptome than can be predicted by its binding sites and that pmtA functions to link metal homeostasis and oxidative stress responses.

Formation of the native beta structure of CRABPI is initiated by rapid hydrophobic collapse, during which local segments of chain adopt significant secondary structure. Subsequently, transient yet specific interactions of amino acid residues restrict the arrangement of the chain topology and initiate long-range associations such as the docking of the N and C termini. The development of native tertiary environments, including the specific packing of the beta-sheet sidechains, occurs in a final, highly cooperative step simultaneous with stable interstrand hydrogen bonding.

"Cluster 9" family lipoproteins function as ligand-binding subunits of ABC-type transporters in maintaining transition metal homeostasis and have been implicated in the virulence of several bacteria. While these proteins share high similarity, the specific metal that they recognize and whether their role in virulence directly involves metal homeostasis cannot be reliably predicted. We examined the cluster 9 protein Lsp of Streptococcus pyogenes and found that specific deletion of lsp produced mutants highly attenuated in a murine model of soft tissue infection. Under standard in vitro conditions, growth of the Lsp ؊ mutant was indistinguishable from that of the wild type, but growth was defective under zinc-limited conditions. The growth defect could be complemented by plasmids expressing wild-type Lsp but not Lsp engineered to lack its putative lipidation residue. Furthermore, Zn 2؉ but not Mn 2؉ rescued Lsp ؊ growth, implicating Zn 2؉ as the physiological ligand for Lsp. Mutation of residues in the putative Zn 2؉ -binding pocket generated variants both hypo-and hyperresistant to zinc starvation, and both mutant classes displayed attenuated virulence. Together, these data suggest that Lsp is a ligand-binding component of an ABC-type zinc permease and that perturbation of zinc homeostasis inhibits the ability of S. pyogenes to cause disease in a zinc-limited host milieu.Transition metals, including iron, zinc, manganese, nickel, and copper, participate in many structural and catalytic functions that are necessary to support the pathogenesis of bacterial infections. However, the ease with which these metals promote cellular electron trafficking also gives them potential to engage in destructive metal-based reactions (25, 59). Thus, a successful pathogen must evolve mechanisms to control the availability and distribution of individual metals within the bacterial cell while exposed to a dynamic host environment with profoundly fluctuating transition metal abundance (13,15,41,62).Evidence is emerging to suggest that the mechanisms by which Streptococcus pyogenes (group A streptococcus) interacts with transition metals play an important role in its ability to cause disease. This gram-positive bacterium is the causative agent of numerous diseases of soft tissue, ranging from selflimiting (e.g., pharyngitis) to destructive and life-threatening (e.g., necrotizing fasciitis), as well as serious postinfectious sequelae such as rheumatic fever and acute glomerulonephritis. A number of metal transporters of S. pyogenes have been characterized, and several of these have been shown to play roles in the virulence of streptococcal infection in various animal models (3,4,40,41,57,70). However, the full repertoire of metal transporters and regulatory elements that comprise the metalloregulatory network of S. pyogenes has not been characterized. In particular, the import and export proteins specific for each of the important transition metals have not been identified. Consequently, global understanding of S. pyogenes transition me...

No abstract

No abstract