text: In their study, Fuhrmann et al. (2009), performed a biochemical and structural analysis of the bacterial transcriptional regulators CtsR/McsB stress response. They sort to clarify and outline the exact function of CtsR and McsB in bacterial stress response. So, they screened proteins from various gram-negative bacteria for recombinant production and succeeded in reconstituting the Bacillus stearothermophilus CtsR/McsB system in vitro. Subsequently, they identified McsB as a protein kinase that targets arginine.