POSTERS - BLAST X - University of Utah

BLAST X Wed. Morning Session
THE CHEMOTACTIC CORE SIGNALLING COMPLEX IS ULTRASTABLE
Annette H. Erbse and Joseph J. Falke
Department of Chemistry and Biochemistry, University of Colorado, Boulder, Campus Box 215,
Boulder, CO 80309
The chemotatic core complex, composed of the transmembrane receptor, the histidinekinase
CheA and the coupling protein CheW, is the central building block of the extensive,
highly cooperative polar signaling clusters in bacteria involved in sensing chemical gradients.
Recent studies have shown that the receptors are organized hexagonal arrays of trimers-ofdimers.
But it is still unclear how these arrays are formed and stabilized, how CheA and CheW
are incorporated into single core complexes and how the complexes are interconnected to build
the cooperative signaling network. Here we focus on the stability of the core complex. We show
that the isolated, membrane-bound core complex is stable for at least 24 hours, both when it is
assembled in vivo and in vitro. All three components are needed to achieve this ultra-stability,
which is dependent on electrostatic interactions. By contrast, the stability is independent of
ligand binding, receptor methylation or kinase activity. We propose that the assembly of the
signaling clusters is cooperative, such that interactions between CheA , CheW and the receptor
trimers-of-dimers are needed not only for receptor regulated kinase activity of individual core
complexes, but also to position neighbouring complexes during the formation of a multi-linked
network. The resulting ultra-stable network is the foundation for the ordered organization and
the hypersensitivity of the signaling patches.
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