Phosphoaspartates in bacterial signal transduction

Bacteria use a strategy referred to as two-component signal transduction to sense a variety of stimuli and initiate an appropriate response. Signal processing begins with proteins referred to as histidine kinases. In most cases, these are membrane-bound receptors that respond to environmental cues. Histidine kinases use ATP as a phosphodonor to phosphorylate a conserved histidine residue. Subsequent transfer of the phosphoryl group to a conserved aspartyl residue in the cognate response regulator results in an appropriate output. Recent structural studies of activated (phosphorylated) response regulators and their aspartate-bearing regulatory domains have provided insight into the links between the chemistry and biology of these ubiquitous regulatory proteins. Chemical aspects of their function appear to generalize broadly to enzymes that adopt a phosphoaspartate intermediate.