Format

Send to

Choose Destination
Mol Microbiol. 2010 Mar;75(5):1171-81. doi: 10.1111/j.1365-2958.2009.07032.x.

Disruption of chemoreceptor signalling arrays by high levels of CheW, the receptor-kinase coupling protein.

Author information

1
Instituto de Investigaciones Biológicas, Universidad Nacional de Mar del Plata, Mar del Plata, Buenos Aires, Argentina.

Abstract

During chemotactic signalling by Escherichia coli, the small cytoplasmic CheW protein couples the histidine kinase CheA to chemoreceptor control. Although essential for assembly and operation of receptor signalling complexes, CheW in stoichiometric excess disrupts chemotactic behaviour. To explore the mechanism of the CheW excess effect, we measured the physiological consequences of high cellular levels of wild-type CheW and of several CheW variants with reduced or enhanced binding affinities for receptor molecules. We found that high levels of CheW interfered with trimer assembly, prevented CheA activation, blocked cluster formation, disrupted chemotactic ability and elevated receptor methylation levels. The severity of these effects paralleled the receptor-binding affinities of the CheW variants. Because trimer formation may be an obligate step in the assembly of ternary signalling complexes and higher-order receptor arrays, we suggest that all CheW excess effects stem from disruption of trimer assembly. We propose that the CheW-binding sites in receptor dimers overlap their trimer contact sites and that high levels of CheW saturate the receptor-binding sites, preventing trimer assembly. The CheW-trapped receptor dimers seem to be improved substrates for methyltransferase reactions, but cannot activate CheA or assemble into clusters, processes that are essential for chemotactic signalling.

PMID:
20487303
PMCID:
PMC5699227
DOI:
10.1111/j.1365-2958.2009.07032.x
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Wiley Icon for PubMed Central
Loading ...
Support Center