Resistance of<i>Neisseria meningitidis</i>to the Toxic Effects of Heme Iron and Other Hydrophobic Agents Requires Expression of<i>ght</i>

Rasmussen, Andrew W.; Alexander, Heather; Perkins-Balding, Donna; Shafer, William M.; Stojiljković, Igor

doi:10.1128/jb.187.15.5214-5223.2005

Cited by 12 publications

(16 citation statements)

References 38 publications

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“…The ⌬ght mutant showed an increased sensitivity to heme (Fig. 1A), confirming the previously reported ght mutant phenotype of another N. meningitidis strain (23). Also, in contrast to the parental strain, the ⌬ght mutant was sensitive to vancomycin and showed a slightly increased sensitivity to tetracycline and chloramphenicol (Fig.…”

Section: Phenotype Of a Ght Mutantsupporting

confidence: 79%

“…Inspection of the sequence of Ght showed that it contains an N-terminal hydrophobic segment, six tetratricopeptide repeat (TPR) domains, and a putative C4-type zinc finger or zinc-binding domain (Fig. 3A) (23). Previously, the N-terminal hydrophobic sequence was suggested to function as a periplasmic targeting signal (23).…”

Section: Phenotype Of a Ght Mutantmentioning

confidence: 99%

“…Rasmussen et al identified a gene, named ght (corresponding to locus tags NMB0339 and NMH_1913 in the genome sequences of strains MC58 [21] and H44/76 [22], respectively), in N. meningitidis whose absence resulted in an increased sensitivity to hydrophobic agents such as heme (23). Such a phenotype is diagnostic for a compromised OM.…”

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confidence: 99%

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Ght Protein of Neisseria meningitidis Is Involved in the Regulation of Lipopolysaccharide Biosynthesis

et al. 2014

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Lipopolysaccharide (LPS) is a major component of the outer membrane of Gram-negative bacteria and is responsible for the barrier function of this membrane. A ght mutant of Neisseria meningitidis that showed increased sensitivity to hydrophobic toxic compounds, suggesting a breach in this permeability barrier, was previously described. Here, we assessed whether this phenotype was possibly caused by a defect in LPS transport or synthesis. The total amount of LPS appeared to be drastically reduced in a ght mutant, but the residual LPS was still detected at the cell surface, suggesting that LPS transport was not impaired. The ght mutant was rapidly overgrown by pseudorevertants that produced normal levels of LPS. Genetic analysis of these pseudorevertants revealed that the lpxC gene, which encodes a key enzyme in LPS synthesis, was fused to the promoter of the upstreamlocated pilE gene, resulting in severe lpxC overexpression. Analysis of phoA and lacZ gene fusions indicated that Ght is an inner membrane protein with an N-terminal membrane anchor and its bulk located in the cytoplasm, where it could potentially interact with LpxC. Cell fractionation experiments indeed indicated that Ght tethers LpxC to the membrane. We suggest that Ght regulates LPS biosynthesis by affecting the activity of LpxC. Possibly, this mechanism acts in the previously observed feedback inhibition of LPS synthesis that occurs when LPS transport is hampered.

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Section: Phenotype Of a Ght Mutantsupporting

confidence: 79%

Section: Phenotype Of a Ght Mutantmentioning

confidence: 99%

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Ght Protein of Neisseria meningitidis Is Involved in the Regulation of Lipopolysaccharide Biosynthesis

et al. 2014

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“…One example of this is the N. meningitidis gene of hydrophobic agent tolerance, ght. The mutation of ght causes increased susceptibility to heme and other hydrophobic agents (91). A broad spectrum of Gram-negative bacteria have ght homologs, including the pathogens E. coli O157:H7, V. cholerae, B. pertussis, Pasteurella multocida, H. influenzae, Salmonella enterica serovar Typhimurium, and Coxiella burnetii (91).…”

Section: Mechanisms Of Bacterial Heme Tolerancementioning

confidence: 99%

“…The mutation of ght causes increased susceptibility to heme and other hydrophobic agents (91). A broad spectrum of Gram-negative bacteria have ght homologs, including the pathogens E. coli O157:H7, V. cholerae, B. pertussis, Pasteurella multocida, H. influenzae, Salmonella enterica serovar Typhimurium, and Coxiella burnetii (91). The mechanism for the increased sensitivity of the ght mutant to heme and other hydrophobic agents has yet to be elucidated; nonetheless, it is separate from the Mtr efflux system and PilQ (91).…”

Section: Mechanisms Of Bacterial Heme Tolerancementioning

confidence: 99%

Overcoming the Heme Paradox: Heme Toxicity and Tolerance in Bacterial Pathogens

2010

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Virtually all bacterial pathogens require iron to infect vertebrates. The most abundant source of iron within vertebrates is in the form of heme as a cofactor of hemoproteins. Many bacterial pathogens have elegant systems dedicated to the acquisition of heme from host hemoproteins. Once internalized, heme is either degraded to release free iron or used intact as a cofactor in catalases, cytochromes, and other bacterial hemoproteins. Paradoxically, the high redox potential of heme makes it a liability, as heme is toxic at high concentrations. Although a variety of mechanisms have been proposed to explain heme toxicity, the mechanisms by which heme kills bacteria are not well understood. Nonetheless, bacteria employ various strategies to protect against and eliminate heme toxicity. Factors involved in heme acquisition and detoxification have been found to contribute to virulence, underscoring the physiological relevance of heme stress during pathogenesis. Herein we describe the current understanding of the mechanisms of heme toxicity and how bacterial pathogens overcome the heme paradox during infection.

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Structure and heme binding properties of Escherichia coli O157:H7 ChuX

et al. 2009

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For many pathogenic microorganisms, iron acquisition from host heme sources stimulates growth, multiplication, ultimately enabling successful survival and colonization. In gramnegative Escherichia coli O157:H7, Shigella dysenteriae and Yersinia enterocolitica the genes encoded within the heme utilization operon enable the effective uptake and utilization of heme as an iron source. While the complement of proteins responsible for heme internalization has been determined in these organisms, the fate of heme once it has reached the cytoplasm has only recently begun to be resolved. Here we report the first crystal structure of ChuX, a member of the conserved heme utilization operon from pathogenic E. coli O157:H7 determined at 2.05 Å resolution. ChuX forms a dimer which remarkably given low sequence homology, displays a very similar fold to the monomer structure of ChuS and HemS, two other heme utilization proteins. Absorption spectral analysis of heme reconstituted ChuX demonstrates that ChuX binds heme in a 1:1 manner implying that each ChuX homodimer has the potential to coordinate two heme molecules in contrast to ChuS and HemS where only one heme molecule is bound. Resonance Raman spectroscopy indicates that the heme of ferric ChuX is composed of a mixture of coordination states: 5-coordinate and high-spin, 6-coordinate and low-spin, and 6-coordinate and high-spin. In contrast, the reduced ferrous form displays mainly a 5-coordinate and high-spin state with a minor contribution from a 6-coordinate and low-spin state. The m Fe-CO and m C-O frequencies of ChuX-bound CO fall on the correlation line expected for histidine-coordinated hemoproteins indicating that the fifth axial ligand of the ferrous heme is the imidazole ring of a histidine residue. Based on sequence and structural comparisons, we designed a number of site-directed mutations in ChuX to probe the heme binding sites and dimer interface. Spectral analysis of ChuX and mutants suggests involvement of H65 and H98 in heme coordination as mutations of both residues were required to abolish the formation of the hexacoordination state of heme-bound ChuX.

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Resistance ofNeisseria meningitidisto the Toxic Effects of Heme Iron and Other Hydrophobic Agents Requires Expression ofght

Cited by 12 publications

References 38 publications

Ght Protein of Neisseria meningitidis Is Involved in the Regulation of Lipopolysaccharide Biosynthesis

Ght Protein of Neisseria meningitidis Is Involved in the Regulation of Lipopolysaccharide Biosynthesis

Overcoming the Heme Paradox: Heme Toxicity and Tolerance in Bacterial Pathogens

Structure and heme binding properties of Escherichia coli O157:H7 ChuX

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