Comparative genomics of Geobacter chemotaxis genes reveals diverse signaling function.

Background: Geobacter species are delta-Proteobacteria and are often the predominant species in a variety of sedimentary environments where Fe(III) reduction is important. Their ability to remediate contaminated environments and produce electricity makes them attractive for further study. Cell motility, biofilm formation, and type IV pili all appear important for the growth of Geobacter in changing environments and for electricity production.

Receptor density balances signal stimulation and attenuation in membrane-assembled complexes of bacterial chemotaxis signaling proteins.

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.

12 Reversible methylation of glutamate residues in the receptor proteins of bacterial sensory systems.

The methyltransferase CheR catalyzes methyl group transfer from S-adenosyl-l-methionine to specific glutamic acid side chains of bacterial chemoreceptors, referred to as the methyl-accepting chemotaxis proteins (MCPs). A second enzyme, the methylesterase CheB, catalyzes ester hydrolysis. Together, CheR and CheB facilitate a reversible receptor methylation process that is essential for sensory adaptation.

Ligand-specific activation of Escherichia coli chemoreceptor transmethylation.

Adaptation in the chemosensory pathways of bacteria like Escherichia coli is mediated by the enzyme-catalyzed methylation (and demethylation) of glutamate residues in the signaling domains of methyl-accepting chemotaxis proteins (MCPs). MCPs can be methylated in trans, where the methyltransferase (CheR) molecule catalyzing methyl group transfer is tethered to the C terminus of a neighboring receptor. Here, it was shown that E.