Novel sigmaB regulation modules of Gram-positive bacteria involve the use of complex hybrid histidine kinases.
A common bacterial strategy to cope with stressful conditions is the activation of alternative sigma factors that control specific regulons enabling targeted responses. In the human pathogen Bacillus cereus, activation of the major stress-responsive sigma factor σ(B) is controlled by a signalling route that involves the multi-sensor hybrid histidine kinase RsbK. RsbK-type kinases are not restricted to the B. cereus group, but occur in a wide variety of other bacterial species, including members of the the low-GC Gram-positive genera Geobacillus and Paenibacillus as well as the high-GC actinobacteria. Genome context and protein sequence analyses of 118 RsbK homologues revealed extreme variability in N-terminal sensory as well as C-terminal regulatory domains and suggested that RsbK-type kinases are subject to complex fine-tuning systems, including sensitization and desensitization via methylation and demethylation within the helical domain preceding the H-box. The RsbK-mediated stress-responsive sigma factor activation mechanism that has evolved in B. cereus and the other species differs markedly from the extensively studied and highly conserved RsbRST-mediated σ(B) activation route found in Bacillus subtilis and other low-GC Gram-positive bacteria. Implications for future research on sigma factor control mechanisms are presented and current knowledge gaps are briefly discussed.
Faculty of Veterinary Medicine, Department of Veterinary Biosciences, Veterinary Microbiology and Epidemiology, University of Helsinki, Helsinki, Finland.|TI Food and Nutrition (TIFN), Wageningen, The Netherlands.|Laboratory of Food Microbiology, Wageningen University and Research Centre, Wageningen, The Netherlands.|Centre for Molecular and Biomolecular Informatics (CMBI), NCMLS, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
Mark
M
de Been
TI Food and Nutrition (TIFN), Wageningen, The Netherlands.|Centre for Molecular and Biomolecular Informatics (CMBI), NCMLS, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
Christof
C
Francke
NIZO food research BV, Ede, The Netherlands.|TI Food and Nutrition (TIFN), Wageningen, The Netherlands.|Centre for Molecular and Biomolecular Informatics (CMBI), NCMLS, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
Roland J
RJ
Siezen
TI Food and Nutrition (TIFN), Wageningen, The Netherlands.|Laboratory of Food Microbiology, Wageningen University and Research Centre, Wageningen, The Netherlands.
Tjakko
T
Abee
D001426:Bacterial Proteins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006094:Gram-Positive Bacteria / Q000502:physiology*; D000071677:Histidine Kinase; D008745:Methylation; D008954:Models, Biological; D010802:Phylogeny; D011494:Protein Kinases / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012808:Sigma Factor / Q000378:metabolism*; D015398:Signal Transduction
D001426:Bacterial Proteins; C079011:SigB protein, Bacteria; D012808:Sigma Factor; D011494:Protein Kinases; D000071677:Histidine Kinase