Characterization of CetA and CetB, a bipartite energy taxis system in <i>Campylobacter jejuni</i>

Elliott, Kathryn T.; DiRita, Victor J.

doi:10.1111/j.1365-2958.2008.06357.x

Cited by 37 publications

(37 citation statements)

References 46 publications

(59 reference statements)

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“…A mutant that is negative for energy taxis is required in order to explore metabolism-independent chemotaxis of C. jejuni. Candidate receptors for sensing of the cellular energy status or redox potential are Tlp6 (Cj0488c), which shows homology to the recently identified energy sensor TlpD of H. pylori (39), and CetA and CetB, which have previously been hypothesized to mediate an energy taxis response of C. jejuni (13,19).…”

Section: Resultsmentioning

confidence: 99%

Energy Taxis Drives Campylobacter jejuni toward the Most Favorable Conditions for Growth

Vegge

Brøndsted

et al. 2009

Appl Environ Microbiol

121

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Campylobacter jejuni is a serious food-borne bacterial pathogen in the developed world. Poultry is a major reservoir, and C. jejuni appears highly adapted to the gastrointestinal tract of birds. Several factors are important for chicken colonization and virulence, including a taxis mechanism for environmental navigation. To explore the mechanism of chemotaxis in C. jejuni, we constructed mutants with deletions of five putative mcp (methyl-accepting chemotaxis protein) genes (tlp1, tlp2, tlp3, docB, and docC). Surprisingly, the deletions did not affect the chemotactic behavior of the mutants compared to that of the parental strain. However, the tlp1, tlp3, docB, and docC mutant strains displayed a 10-fold decrease in the ability to invade human epithelial and chicken embryo cells, hence demonstrating that the corresponding proteins affect the host interaction. LAsparagine, formate, D-lactate, and chicken mucus were identified as new attractants of C. jejuni, and we observed that chemical substances promoting tactic attraction are all known to support the growth of this organism. The attractants could be categorized as carbon sources and electron donors and acceptors, and we furthermore observed a correlation between an attractant's potency and its efficiency as an energy source. The tactic attraction was inhibited by the respiratory inhibitors HQNO (2-n-heptyl-4-hydroxyquinoline N-oxide) and sodium azide, which significantly reduce energy production by oxidative phosphorylation. These findings strongly indicate that energy taxis is the primary force in environmental navigation by C. jejuni and that this mechanism drives the organism toward the optimal chemical conditions for energy generation and colonization.

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Section: Resultsmentioning

confidence: 99%

Energy Taxis Drives Campylobacter jejuni toward the Most Favorable Conditions for Growth

Vegge

Brøndsted

et al. 2009

Appl Environ Microbiol

121

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“…Thereby, CetB senses changes in the redox state of the electron transport system and transmits this signal to CetA via direct interaction. From CetA, the signal is transduced to the chemotactic machinery, which in turn changes the direction of motility (Hendrixson et al, 2001;Elliott & DiRita, 2008). Energy taxis has been shown to be an important force driving C. jejuni towards attractants that serve as carbon sources, electron acceptors and, as in the case of formic acid, electron donors (Vegge et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

Campylobacter jejuni proteins Cj0952c and Cj0951c affect chemotactic behaviour towards formic acid and are important for invasion of host cells

et al. 2010

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Campylobacter jejuni, an important food-borne bacterial pathogen in industrialized countries and in the developing world, is one of the major causes of bacterial diarrhoea. To identify genes which are important for the invasion of host cells by the pathogen, we screened altogether 660 clones of a transposon-generated mutant library based on the clinical C. jejuni isolate B2. Thereby, we identified a clone with a transposon insertion in gene cj0952c. As in the well-characterized C. jejuni strain NCTC 11168, the corresponding protein together with the gene product of the adjacent gene cj0951c consists of two transmembrane domains, a HAMP domain and a putative MCP domain, which together are thought to act as a chemoreceptor, designated Tlp7. In this report we show that genes cj0952c and cj0951c (i) are important for the host cell invasion of the pathogen, (ii) are not translated as one protein in C. jejuni isolate B2, contradicting the idea of a postulated read-through mechanism, (iii) affect the motility of C. jejuni, (iv) alter the chemotactic behaviour of the pathogen towards formic acid, and (v) are not related to the utilization of formic acid by formate dehydrogenase.

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“…If CetA and CetB function solely as partners to transduce an energy taxis signal, we would expect the ⌬cetA and ⌬cetB mutants to have similar phenotypes. It should be noted that CetB levels are quite low in the ⌬cetA mutant (19). However, the lack of an invasion defect in the ⌬cetB mutant directly rules out a role for CetB in invasion.…”

Section: Vol 191 2009 Hamp/pas Families Of Signal Transduction Protmentioning

confidence: 99%

“…These proteins were also assessed for the presence of transmembrane domains using the DAS (dense alignment surface) method (17). Proteins predicted to contain one long transmembrane helix with a strong dip in hydrophobicity in the middle of this region, corresponding to helical hairpin residues (42,43), were designated as possessing two transmembrane domains on the basis of topology analysis of CetA (19). The GϩC percentage of each HAMP-containing bipartite family member gene was plotted against the GϩC percentage of the genome in which it was found.…”

Section: Methodsmentioning

confidence: 99%

Conserved Residues in the HAMP Domain Define a New Family of Proposed Bipartite Energy Taxis Receptors

Elliott¹,

Zhulin

Stuckey³

et al. 2009

J Bacteriol

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HAMP domains, found in many bacterial signal transduction proteins, generally transmit an intramolecular signal between an extracellular sensory domain and an intracellular signaling domain. Studies of HAMP domains in proteins where both the input and output signals occur intracellularly are limited to those of the Aer energy taxis receptor of Escherichia coli, which has both a HAMP domain and a sensory PAS domain. Campylobacter jejuni has an energy taxis system consisting of the domains of Aer divided between two proteins, CetA (HAMP domain containing) and CetB (PAS domain containing). In this study, we found that the CetA HAMP domain differs significantly from that of Aer in the predicted secondary structure. Using similarity searches, we identified 55 pairs of HAMP/PAS proteins encoded by adjacent genes in a diverse group of microorganisms. We propose that these HAMP/PAS pairs form a new family of bipartite energy taxis receptors. Within these proteins, we identified nine residues in the HAMP domain and proximal signaling domain that are highly conserved, at least three of which are required for CetA function. Additionally, we demonstrated that CetA contributes to the invasion of human epithelial cells by C. jejuni, while CetB does not. This finding supports the hypothesis that members of HAMP/PAS pairs possess the capacity to act independently of each other in cellular traits other than energy taxis.HAMP domains (named for their presence in histidine kinases, adenylyl cyclases, methyl-accepting chemotaxis proteins, and phosphatases) (6) represent a common element in numerous bacterial signal transduction proteins. More than 11,700 known or predicted proteins containing HAMP domains are identified in the SMART database (39). The vast majority of these proteins are eubacterial, but HAMP domains have also been identified in archaea and lower eukaryotic organisms. HAMP domains are thought to play a role in intramolecular communication between the input and output domains of a single protein (4-6). HAMP domains have been studied predominantly in transmembrane receptors that translate a signal originating extracellularly to an intracellular signal transduction domain.Our understanding of how HAMP domains function has been hampered by considerable sequence divergence among these domains and a paucity of structural data. Sequence analysis and mutagenesis studies have indicated that HAMP domains consist of two amphipathic helices (AS-1 and AS-2), which are joined by a flexible loop region to form a coiled-coil (5, 14, 47). Recently, the structure of the HAMP domain from the Archaeoglobus fulgidus protein Af1503 was solved (31). Af1503 is atypical of HAMP domain-containing proteins in that it lacks an output signal transduction domain (31). This structure consists of two amphipathic helices that come together in a parallel coiled-coil. These helices form a four-helix bundle in a HAMP domain dimer. This four-helix bundle adopts an unusual knobs-to-knobs conformation. These findings gave rise to a model where a shift in...

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Characterization of CetA and CetB, a bipartite energy taxis system in Campylobacter jejuni

Cited by 37 publications

References 46 publications

Energy Taxis Drives Campylobacter jejuni toward the Most Favorable Conditions for Growth

Energy Taxis Drives Campylobacter jejuni toward the Most Favorable Conditions for Growth

Campylobacter jejuni proteins Cj0952c and Cj0951c affect chemotactic behaviour towards formic acid and are important for invasion of host cells

Conserved Residues in the HAMP Domain Define a New Family of Proposed Bipartite Energy Taxis Receptors

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