POSTERS - BLAST X - University of Utah

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