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Identification of Archaea-specific chemotaxis proteins which interact with the flagellar apparatus.

Schlesner M, Miller A, Streif S, Staudinger WF, Müller J, Scheffer B, Siedler F, Oesterhelt D - BMC Microbiol. (2009)

Bottom Line: Deletion of the second DUF439 protein had only minimal effects.Genes coding for DUF439 proteins, however, were found to be integral parts of chemotaxis gene regions across the archaeal domain, and they were not detected in other genomic context.Altogether, these results demonstrate that, in the archaeal domain, previously unrecognized archaea-specific Che proteins are essential for relaying taxis signaling to the flagellar apparatus.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Membrane Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany. schlesne@biochem.mpg.de

ABSTRACT

Background: Archaea share with bacteria the ability to bias their movement towards more favorable locations, a process known as taxis. Two molecular systems drive this process: the motility apparatus and the chemotaxis signal transduction system. The first consists of the flagellum, the flagellar motor, and its switch, which allows cells to reverse the rotation of flagella. The second targets the flagellar motor switch in order to modulate the switching frequency in response to external stimuli. While the signal transduction system is conserved throughout archaea and bacteria, the archaeal flagellar apparatus is different from the bacterial one. The proteins constituting the flagellar motor and its switch in archaea have not yet been identified, and the connection between the bacterial-like chemotaxis signal transduction system and the archaeal motility apparatus is unknown.

Results: Using protein-protein interaction analysis, we have identified three proteins in Halobacterium salinarum that interact with the chemotaxis (Che) proteins CheY, CheD, and CheC2, as well as the flagella accessory (Fla) proteins FlaCE and FlaD. Two of the proteins belong to the protein family DUF439, the third is a HEAT_PBS family protein. In-frame deletion strains for all three proteins were generated and analyzed as follows: a) photophobic responses were measured by a computer-based cell tracking system b) flagellar rotational bias was determined by dark-field microscopy, and c) chemotactic behavior was analyzed by a swarm plate assay. Strains deleted for the HEAT_PBS protein or one of the DUF439 proteins proved unable to switch the direction of flagellar rotation. In these mutants, flagella rotate only clockwise, resulting in exclusively forward swimming cells that are unable to respond to tactic signals. Deletion of the second DUF439 protein had only minimal effects. HEAT_PBS proteins could be identified in the chemotaxis gene regions of all motile haloarchaea sequenced so far, but not in those of other archaeal species. Genes coding for DUF439 proteins, however, were found to be integral parts of chemotaxis gene regions across the archaeal domain, and they were not detected in other genomic context.

Conclusion: Altogether, these results demonstrate that, in the archaeal domain, previously unrecognized archaea-specific Che proteins are essential for relaying taxis signaling to the flagellar apparatus.

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Organization of chemotaxis genes in archaeal genomes. Known chemotaxis genes (indicated by gene letter) and genes coding for receptors (Methyl-accepting chemotaxis proteins, MCP) are shown in blue. Genes coding for proteins of the family DUF439 are shown in light blue and genes coding for HEAT domain proteins in cyan. Gray indicates that, where no name is given, the function of the coded protein is unknown, or the protein is probably unrelated to chemotaxis (S6: 30S ribosomal protein S6e). A//sign indicates separated genome regions. The asterisk indicates that this protein is interrupted by a frame-shift mutation.
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Figure 5: Organization of chemotaxis genes in archaeal genomes. Known chemotaxis genes (indicated by gene letter) and genes coding for receptors (Methyl-accepting chemotaxis proteins, MCP) are shown in blue. Genes coding for proteins of the family DUF439 are shown in light blue and genes coding for HEAT domain proteins in cyan. Gray indicates that, where no name is given, the function of the coded protein is unknown, or the protein is probably unrelated to chemotaxis (S6: 30S ribosomal protein S6e). A//sign indicates separated genome regions. The asterisk indicates that this protein is interrupted by a frame-shift mutation.

Mentions: Homology searches showed that no members of the family DUF439 can be found outside the domain Archaea. Among the archaea, the presence of such a gene strictly correlated with the presence of che genes (see Additional file 6). The only exceptions were Methanocaldococcus jannaschii, which does not possess che genes but has a DUF439 homolog, and Methanosarcina barkeri, that has che genes but no DUF439. Examination of the genomic context revealed that the DUF439 genes are always located in the chemotaxis gene regions (Figure 5). The exceptions were two of the four paralogs in H. marismortui. In 10 out of 17 species the DUF439 gene is adjacent to CheY.


Identification of Archaea-specific chemotaxis proteins which interact with the flagellar apparatus.

Schlesner M, Miller A, Streif S, Staudinger WF, Müller J, Scheffer B, Siedler F, Oesterhelt D - BMC Microbiol. (2009)

Organization of chemotaxis genes in archaeal genomes. Known chemotaxis genes (indicated by gene letter) and genes coding for receptors (Methyl-accepting chemotaxis proteins, MCP) are shown in blue. Genes coding for proteins of the family DUF439 are shown in light blue and genes coding for HEAT domain proteins in cyan. Gray indicates that, where no name is given, the function of the coded protein is unknown, or the protein is probably unrelated to chemotaxis (S6: 30S ribosomal protein S6e). A//sign indicates separated genome regions. The asterisk indicates that this protein is interrupted by a frame-shift mutation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2666748&req=5

Figure 5: Organization of chemotaxis genes in archaeal genomes. Known chemotaxis genes (indicated by gene letter) and genes coding for receptors (Methyl-accepting chemotaxis proteins, MCP) are shown in blue. Genes coding for proteins of the family DUF439 are shown in light blue and genes coding for HEAT domain proteins in cyan. Gray indicates that, where no name is given, the function of the coded protein is unknown, or the protein is probably unrelated to chemotaxis (S6: 30S ribosomal protein S6e). A//sign indicates separated genome regions. The asterisk indicates that this protein is interrupted by a frame-shift mutation.
Mentions: Homology searches showed that no members of the family DUF439 can be found outside the domain Archaea. Among the archaea, the presence of such a gene strictly correlated with the presence of che genes (see Additional file 6). The only exceptions were Methanocaldococcus jannaschii, which does not possess che genes but has a DUF439 homolog, and Methanosarcina barkeri, that has che genes but no DUF439. Examination of the genomic context revealed that the DUF439 genes are always located in the chemotaxis gene regions (Figure 5). The exceptions were two of the four paralogs in H. marismortui. In 10 out of 17 species the DUF439 gene is adjacent to CheY.

Bottom Line: Deletion of the second DUF439 protein had only minimal effects.Genes coding for DUF439 proteins, however, were found to be integral parts of chemotaxis gene regions across the archaeal domain, and they were not detected in other genomic context.Altogether, these results demonstrate that, in the archaeal domain, previously unrecognized archaea-specific Che proteins are essential for relaying taxis signaling to the flagellar apparatus.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Membrane Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany. schlesne@biochem.mpg.de

ABSTRACT

Background: Archaea share with bacteria the ability to bias their movement towards more favorable locations, a process known as taxis. Two molecular systems drive this process: the motility apparatus and the chemotaxis signal transduction system. The first consists of the flagellum, the flagellar motor, and its switch, which allows cells to reverse the rotation of flagella. The second targets the flagellar motor switch in order to modulate the switching frequency in response to external stimuli. While the signal transduction system is conserved throughout archaea and bacteria, the archaeal flagellar apparatus is different from the bacterial one. The proteins constituting the flagellar motor and its switch in archaea have not yet been identified, and the connection between the bacterial-like chemotaxis signal transduction system and the archaeal motility apparatus is unknown.

Results: Using protein-protein interaction analysis, we have identified three proteins in Halobacterium salinarum that interact with the chemotaxis (Che) proteins CheY, CheD, and CheC2, as well as the flagella accessory (Fla) proteins FlaCE and FlaD. Two of the proteins belong to the protein family DUF439, the third is a HEAT_PBS family protein. In-frame deletion strains for all three proteins were generated and analyzed as follows: a) photophobic responses were measured by a computer-based cell tracking system b) flagellar rotational bias was determined by dark-field microscopy, and c) chemotactic behavior was analyzed by a swarm plate assay. Strains deleted for the HEAT_PBS protein or one of the DUF439 proteins proved unable to switch the direction of flagellar rotation. In these mutants, flagella rotate only clockwise, resulting in exclusively forward swimming cells that are unable to respond to tactic signals. Deletion of the second DUF439 protein had only minimal effects. HEAT_PBS proteins could be identified in the chemotaxis gene regions of all motile haloarchaea sequenced so far, but not in those of other archaeal species. Genes coding for DUF439 proteins, however, were found to be integral parts of chemotaxis gene regions across the archaeal domain, and they were not detected in other genomic context.

Conclusion: Altogether, these results demonstrate that, in the archaeal domain, previously unrecognized archaea-specific Che proteins are essential for relaying taxis signaling to the flagellar apparatus.

Show MeSH
Related in: MedlinePlus