The potassium-sensory mechanism of a prokaryotic histidine kinase/response regulator system

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Bacteria sense and respond to various stress conditions by employing so called two-component systems. These systems consist of a histidine kinase and a response regulator, which sense environmental stimuli, transduce information via phosphorylation and induce a cellular response. Escherichia coli, for example, contains 32 of these systems. One of which, the K+-responsive KdpD/KdpE-system, is encoded in more than 1000 sequenced bacterial and archaeal genomes including many pathogenic organisms. KdpD will be used as representative of the sensor histidine kinase family to obtain insights into protein structure and dynamics during sensing and signaling. Therefore, it will be the aim of the project to elucidate the structural basis and the molecular mechanism of K+-sensing in KdpD. The 3D-structure of full-length KdpD and of separated domains shall be resolved. Furthermore, we shall test a new stimulus perception model for KdpD, the dual K+-binding site model. Finally, conformational dynamics during signaling within the histidine kinase shall be monitored using a Foerster resonance energy transfer (FRET)-based approach. Work on this project will contribute both to a better understanding of the molecular mechanism of a K+-responsive histidine kinase as well to the elucidation of K+-binding motifs in proteins in general.