POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
<strong>BLAST</strong> X Wed. Morning Session<br />
THE CHEMOTACTIC CORE SIGNALLING COMPLEX IS ULTRASTABLE<br />
Annette H. Erbse and Joseph J. Falke<br />
Department <strong>of</strong> Chemistry and Biochemistry, <strong>University</strong> <strong>of</strong> Colorado, Boulder, Campus Box 215,<br />
Boulder, CO 80309<br />
The chemotatic core complex, composed <strong>of</strong> the transmembrane receptor, the histidinekinase<br />
CheA and the coupling protein CheW, is the central building block <strong>of</strong> the extensive,<br />
highly cooperative polar signaling clusters in bacteria involved in sensing chemical gradients.<br />
Recent studies have shown that the receptors are organized hexagonal arrays <strong>of</strong> trimers-<strong>of</strong>dimers.<br />
But it is still unclear how these arrays are formed and stabilized, how CheA and CheW<br />
are incorporated into single core complexes and how the complexes are interconnected to build<br />
the cooperative signaling network. Here we focus on the stability <strong>of</strong> the core complex. We show<br />
that the isolated, membrane-bound core complex is stable for at least 24 hours, both when it is<br />
assembled in vivo and in vitro. All three components are needed to achieve this ultra-stability,<br />
which is dependent on electrostatic interactions. By contrast, the stability is independent <strong>of</strong><br />
ligand binding, receptor methylation or kinase activity. We propose that the assembly <strong>of</strong> the<br />
signaling clusters is cooperative, such that interactions between CheA , CheW and the receptor<br />
trimers-<strong>of</strong>-dimers are needed not only for receptor regulated kinase activity <strong>of</strong> individual core<br />
complexes, but also to position neighbouring complexes during the formation <strong>of</strong> a multi-linked<br />
network. The resulting ultra-stable network is the foundation for the ordered organization and<br />
the hypersensitivity <strong>of</strong> the signaling patches.<br />
35