Dynamic clustering of the bacterial sensory kinase BaeS

Several bacterial sensory-kinase receptors form clusters on the cell membrane. However, the dynamics of sensory-kinase clustering are largely unclear. Using measurements of fluorescence anisotropy and time-lapse imaging of Escherichia coli cells, we demonstrate that copper ions trigger self-association of BaeS receptors and lead to rapid formation of clusters, which can be reversibly dispersed by a metal chelator. Copper ions did not trigger selfassociation of other fluorescently tagged sensory kinases, and other divalent metal ions could not elicit self-association of BaeS. The histidine residues in the BaeS periplasmic domain are essential for copper binding in vitro and are important for the copper-induced BaeS responses in vivo. BaeS clustering was triggered also under conditions that directly triggered BaeS-dependent transcriptional responses. Thus, clustering of sensory kinase receptors can be dynamic and context dependent and can be triggered by specific environmental cues.