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J. Mol. Micro. Biotechnol. 4: 223-228
Towards an Understanding of the Molecular Mechanisms of Stimulus Perception and Signal Transduction by the KdpD/KdpE System of Escherichia coli
Kirsten Jung and Karlheinz Altendorf
The membrane-bound histidine kinase KdpD is a putative turgor sensor that regulates, together with the response regulator KdpE, expression of the kdpFABC operon. This operon encodes the high affinity K+-uptake system KdpFABC of Escherichia coli. Expression of kdpFABC is induced under K+ limiting growth conditions and in response to an osmotic upshift. Various structural features of KdpD and KdpE, which are important for stimulus perception and/or signal transduction were identified and are described here. Furthermore, various studies undertaken to elucidate the nature of the stimulus for KdpD result in a new model for KdpD stimulus perception. According to this, autophosphorylation activity of KdpD is not a result of changes in turgor per se. Instead, various -- mainly intracellular parameters -- that are related to changes of environmental conditions influence the activities of KdpD.
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