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

Elliott KT, Dirita VJ - Mol. Microbiol. (2008)

Bottom Line: The PAS domain (a sensory domain named after three proteins Per, ARNT and Sim, where it was first identified) is thought to interact directly with the Aer HAMP domain to transmit this signal to the highly conserved domain (HCD) found in chemotaxis receptors.CetA has two transmembrane helices in a helical hairpin while CetB is a peripheral membrane protein tightly associated with the membrane.This study provides a foundation for further characterization of signal transduction mechanisms within CetA/CetB.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA.

ABSTRACT
The energy taxis receptor Aer, in Escherichia coli, senses changes in the redox state of the electron transport system via an flavin adenine dinucleotide cofactor bound to a PAS domain. The PAS domain (a sensory domain named after three proteins Per, ARNT and Sim, where it was first identified) is thought to interact directly with the Aer HAMP domain to transmit this signal to the highly conserved domain (HCD) found in chemotaxis receptors. An apparent energy taxis system in Campylobacter jejuni is composed of two proteins, CetA and CetB, that have the domains of Aer divided between them. CetB has a PAS domain, while CetA has a predicted transmembrane region, HAMP domain and the HCD. In this study, we examined the expression of cetA and cetB and the biochemical properties of the proteins they encode. cetA and cetB are co-transcribed independently of the flagellar regulon. CetA has two transmembrane helices in a helical hairpin while CetB is a peripheral membrane protein tightly associated with the membrane. CetB levels are CetA dependent. Additionally, we demonstrated that both CetA and CetB participate in complexes, including a likely CetB dimer and a complex that may include both CetA and CetB. This study provides a foundation for further characterization of signal transduction mechanisms within CetA/CetB.

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Expression of CetA and CetB in various genetic backgrounds.A. Whole-cell extracts were prepared from wild type, ΔcetB, ΔcetA, ΔcetAB, ΔrpoN and ΔfliA. These were separated by 12.5% SDS-PAGE and CetA and CetB detected by immunoblotting.B. Whole cell extracts were prepared from ΔcetB and ΔcetAB with pECO101, pECO101::cetB, pECO101::cetAB, pRY108, pRY108::cetAB or pRY108::cetA(Y116A)cetB. These samples were separated by 12.5% SDS-PAGE and CetA and CetB detected by immunoblotting.
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fig02: Expression of CetA and CetB in various genetic backgrounds.A. Whole-cell extracts were prepared from wild type, ΔcetB, ΔcetA, ΔcetAB, ΔrpoN and ΔfliA. These were separated by 12.5% SDS-PAGE and CetA and CetB detected by immunoblotting.B. Whole cell extracts were prepared from ΔcetB and ΔcetAB with pECO101, pECO101::cetB, pECO101::cetAB, pRY108, pRY108::cetAB or pRY108::cetA(Y116A)cetB. These samples were separated by 12.5% SDS-PAGE and CetA and CetB detected by immunoblotting.

Mentions: Campylobacter jejuni has only three known sigma factors identified within its genome: σ70, σ54 (encoded by rpoN) and σ28 (encoded by fliA). The latter two sigma factors are required for the flagellar transcriptional cascade in C. jejuni (Hendrixson and DiRita, 2003). Levels of CetA and CetB were unaffected in strains lacking σ54 or σ28, indicating that cetA and cetB are likely expressed in a σ70-dependent fashion (Fig. 2A).


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

Elliott KT, Dirita VJ - Mol. Microbiol. (2008)

Expression of CetA and CetB in various genetic backgrounds.A. Whole-cell extracts were prepared from wild type, ΔcetB, ΔcetA, ΔcetAB, ΔrpoN and ΔfliA. These were separated by 12.5% SDS-PAGE and CetA and CetB detected by immunoblotting.B. Whole cell extracts were prepared from ΔcetB and ΔcetAB with pECO101, pECO101::cetB, pECO101::cetAB, pRY108, pRY108::cetAB or pRY108::cetA(Y116A)cetB. These samples were separated by 12.5% SDS-PAGE and CetA and CetB detected by immunoblotting.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2628428&req=5

fig02: Expression of CetA and CetB in various genetic backgrounds.A. Whole-cell extracts were prepared from wild type, ΔcetB, ΔcetA, ΔcetAB, ΔrpoN and ΔfliA. These were separated by 12.5% SDS-PAGE and CetA and CetB detected by immunoblotting.B. Whole cell extracts were prepared from ΔcetB and ΔcetAB with pECO101, pECO101::cetB, pECO101::cetAB, pRY108, pRY108::cetAB or pRY108::cetA(Y116A)cetB. These samples were separated by 12.5% SDS-PAGE and CetA and CetB detected by immunoblotting.
Mentions: Campylobacter jejuni has only three known sigma factors identified within its genome: σ70, σ54 (encoded by rpoN) and σ28 (encoded by fliA). The latter two sigma factors are required for the flagellar transcriptional cascade in C. jejuni (Hendrixson and DiRita, 2003). Levels of CetA and CetB were unaffected in strains lacking σ54 or σ28, indicating that cetA and cetB are likely expressed in a σ70-dependent fashion (Fig. 2A).

Bottom Line: The PAS domain (a sensory domain named after three proteins Per, ARNT and Sim, where it was first identified) is thought to interact directly with the Aer HAMP domain to transmit this signal to the highly conserved domain (HCD) found in chemotaxis receptors.CetA has two transmembrane helices in a helical hairpin while CetB is a peripheral membrane protein tightly associated with the membrane.This study provides a foundation for further characterization of signal transduction mechanisms within CetA/CetB.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA.

ABSTRACT
The energy taxis receptor Aer, in Escherichia coli, senses changes in the redox state of the electron transport system via an flavin adenine dinucleotide cofactor bound to a PAS domain. The PAS domain (a sensory domain named after three proteins Per, ARNT and Sim, where it was first identified) is thought to interact directly with the Aer HAMP domain to transmit this signal to the highly conserved domain (HCD) found in chemotaxis receptors. An apparent energy taxis system in Campylobacter jejuni is composed of two proteins, CetA and CetB, that have the domains of Aer divided between them. CetB has a PAS domain, while CetA has a predicted transmembrane region, HAMP domain and the HCD. In this study, we examined the expression of cetA and cetB and the biochemical properties of the proteins they encode. cetA and cetB are co-transcribed independently of the flagellar regulon. CetA has two transmembrane helices in a helical hairpin while CetB is a peripheral membrane protein tightly associated with the membrane. CetB levels are CetA dependent. Additionally, we demonstrated that both CetA and CetB participate in complexes, including a likely CetB dimer and a complex that may include both CetA and CetB. This study provides a foundation for further characterization of signal transduction mechanisms within CetA/CetB.

Show MeSH
Related in: MedlinePlus