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Journal of Bacteriology, December 2001, p. 7135-7144, Vol. 183, No. 24
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.24.7135-7144.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

CheR- and CheB-Dependent Chemosensory Adaptation System of Rhodobacter sphaeroides

Angela C. Martin, George H. Wadhams, Deepan S. H. Shah,dagger Steven L. Porter, Jeevani C. Mantotta, Tim J. Craig, Peter H. Verdult, Helen Jones, and Judith P. Armitage*

Microbiology Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom

Received 25 June 2001/Accepted 18 September 2001

Rhodobacter sphaeroides has multiple homologues of most of the Escherichia coli chemotaxis genes, organized in three major operons and other, unlinked, loci. These include cheA1 and cheR1 (che Op1) and cheA2, cheR2, and cheB1 (che Op2). In-frame deletions of these cheR and cheB homologues were constructed and the chemosensory behaviour of the resultant mutants examined on swarm plates and in tethered cell assays. Under the conditions tested, CheR2 and CheB1 were essential for normal chemotaxis, whereas CheR1 was not. cheR2 and cheB1, but not cheR1, were also able to complement the equivalent E. coli mutants. However, none of the proteins were required for the correct polar localization of the chemoreceptor McpG in R. sphaeroides. In E. coli, CheR binds to the NWETF motif on the high-abundance receptors, allowing methylation of both high- and low-abundance receptors. This motif is not contained on any R. sphaeroides chemoreceptors thus far identified, although 2 of the 13 putative chemoreceptors, McpA and TlpT, do have similar sequences. This suggests that CheR2 either interacts with the NWETF motif of E. coli methyl-accepting chemotaxis proteins (MCPs), even though its native motif may be slightly different, or with another conserved region of the MCPs. Methanol release measurements show that R. sphaeroides has an adaptation system that is different from that of Bacillus subtilis and E. coli, with methanol release measurable on the addition of attractant but not on its removal. Intriguingly, CheA2, but not CheA1, is able to phosphorylate CheB1, suggesting that signaling through CheA1 cannot initiate feedback receptor adaptation via CheB1-P.

* Corresponding author. Mailing address: Microbiology Unit, Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, United Kingdom. Phone: 44-1865-275299. Fax: 44-1865-275297. E-mail: armitage{at}bioch.ox.ac.uk.

dagger Present address: Department of Oral Biology, Dental School, University of Newcastle, Newcastle-upon-Tyne NE2 4BW, United Kingdom.

Journal of Bacteriology, December 2001, p. 7135-7144, Vol. 183, No. 24
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.24.7135-7144.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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Copyright © 2001 by the American Society for Microbiology. All rights reserved.