POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
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<strong>BLAST</strong> X Thurs. Evening Session<br />
MINOR RECEPTOR SIGNALLING IN E. COLI<br />
Silke Neumann, Ned Wingreen* and Victor Sourjik<br />
Ruprecht-Karls-Universität Heidelberg, Zentrum für molekulare Biologie Heidelberg (ZMBH), Im<br />
Neuenheimer Feld 282, 69120 Heidelberg, Germany<br />
* Department <strong>of</strong> Molecular Biology - Princeton <strong>University</strong><br />
Ligand recognition in the chemotaxis pathway <strong>of</strong> E. coli proceeds through binding <strong>of</strong><br />
ligands to transmembrane receptors, either directly or indirectly through periplasmic binding<br />
proteins. E. coli has five types <strong>of</strong> receptors, with two high-abundance (or major) receptors – Tsr<br />
for serine and Tar for aspartate and maltose – and three low-abundance (or minor) receptors –<br />
Tap for dipeptides, Trg for ribose, galactose and glucose, and Aer for redox potential. Together<br />
with the histidine kinase CheA, receptors form chemosensory complexes which in turn are<br />
organized in tight clusters where receptors <strong>of</strong> different ligand specificities are intermixed. Signal<br />
processing is thought to occur within these receptor clusters through allosteric interactions<br />
between receptor dimers. To compare signal processing by minor and major receptors, we<br />
systematically investigated responses mediated by Trg and Tap, and by Tar and Tsr in respect<br />
to response sensitivity, relation between receptor occupancy and kinase inactivation, dynamic<br />
range <strong>of</strong> the response, adaptation time to a range <strong>of</strong> stimuli, as well as integration <strong>of</strong> signals that<br />
are sensed by different receptors using an in vivo FRET-based kinase assay. Our experimental<br />
analysis shows that signals are amplified and integrated differently by the two receptor<br />
populations, but in both cases signal processing can be quantitatively explained by the same<br />
allosteric model.<br />
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