title: Receptor density balances signal stimulation and attenuation in membrane-assembled complexes of bacterial chemotaxis signaling proteins.
abstract: All cells possess transmembrane signaling systems that function in the environment of the lipid bilayer. In the Escherichia coli chemotaxis pathway, the binding of attractants to a two-dimensional array of receptors and signaling proteins simultaneously inhibits an associated kinase and stimulates receptor methylation--a slower process that restores kinase activity. These two opposing effects lead to robust adaptation toward stimuli through a physical mechanism that is not understood. Here, we provide evidence of a counterbalancing influence exerted by receptor density on kinase stimulation and receptor methylation. Receptor signaling complexes were reconstituted over a range of defined surface concentrations by using a template-directed assembly method, and the kinase and receptor methylation activities were measured. Kinase activity and methylation rates were both found to vary significantly with surface concentration--yet in opposite ways: samples prepared at high surface densities stimulated kinase activity more effectively than low-density samples, whereas lower surface densities produced greater methylation rates than higher densities. FRET experiments demonstrated that the cooperative change in kinase activity coincided with a change in the arrangement of the membrane-associated receptor domains. The counterbalancing influence of density on receptor methylation and kinase stimulation leads naturally to a model for signal regulation that is compatible with the known logic of the E. coli pathway. Density-dependent mechanisms are likely to be general and may operate when two or more membrane-related processes are influenced differently by the two-dimensional concentration of pathway elements.
authors: Department of Chemistry, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003-9336, USA.
authors: Tatiana Y
authors: TY
authors: Besschetnova
authors: David J
authors: DJ
authors: Montefusco
authors: Abdalin E
authors: AE
authors: Asinas
authors: Anthony L
authors: AL
authors: Shrout
authors: Frances M
authors: FM
authors: Antommattei
authors: Robert M
authors: RM
authors: Weis
mesh_terms: D001426:Bacterial Proteins; D002633:Chemotaxis; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D008745:Methylation; D046912:Multiprotein Complexes; D011494:Protein Kinases; D011956:Receptors, Cell Surface; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; C489103:CheW protein, E coli; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D046912:Multiprotein Complexes; D011956:Receptors, Cell Surface; D011494:Protein Kinases