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The heme-binding protein HbpS regulates the activity of the Streptomyces reticuli iron-sensing histidine kinase SenS in a redox-dependent manner

Bogel, Gabriele, Schrempf, Hildgund, Ortiz de Orué Lucana, Darío
Amino acids 2009 v.37 no.4 pp. 681-691
Streptomyces reticuli, heme, histidine kinase, hydrogen peroxide, ions, mutants, phosphorylation
The SenS/SenR system of Streptomyces reticuli regulates the expression of the redox regulator FurS, the catalase-peroxidase CpeB and the heme-binding protein HbpS. SenS/SenR is also proposed to participate in sensing redox changes, mediated by HbpS. Here, we show in vitro that heme-free HbpS represses the autokinase activity of SenS; whereas hemin-treated HbpS considerably enhances SenS autophosphorylation under redox conditions using either H₂O₂ or DTT. The presence of iron ions alone or in combination with H₂O₂ or DTT also leads to significantly increased phosphorylation levels of SenS. Further comparative physiological studies using the S. reticuli WT, a S. reticuli hbpS mutant and a S. reticuli senS-senR mutant corroborates the importance of HbpS and the SenS/SenR system for resistance against high concentrations of iron ions and hemin in vivo. Hence SenS/SenR and HbpS act in concert as a novel three-component system which detects redox stress, mediated by iron ions and heme.