Two-component Signaling in the Gram-positive Envelope Stress Response: Intramembrane-sensing Histidine Kinases and Accessory Membrane Proteins
Karen Schrecke, Anna Staroń and Thorsten Mascher
from: Two-Component Systems in Bacteria (Edited by: Roy Gross and Dagmar Beier). Caister Academic Press, U.K. (2012)
The cell envelope stress response (CESR) network monitors and maintains envelope integrity to counteract the damaging effects of cell wall antibiotics and membrane perturbating agents. Two-component systems (2CSs) involved in orchestrating CESR in Firmicutes bacteria (low G+C Gram-positive) are characterized by so-called intramembrane-sensing histidine kinases (IM-HKs). The N-terminal input domain of these proteins consists of two transmembrane helices with a very short extracellular linker of less than 20 amino acids, which is insufficient for stimulus perception. It was originally thought that these HKs sense their stimuli within the membrane interface. But subsequent studies identified accessory membrane proteins for all IM-HKs described so far. This chapter will specifically summarize the current state of knowledge on BceRS- and LiaRS-like 2CSs, which are ubiquitously distributed in Firmicutes bacteria. While BceRSAB-like systems represent antibiotic-specific detoxification modules, LiaFSR-like three-component systems mount more general CESR. These two types of systems are genetically and functionally linked to BceAB-like ABC transporters and LiaF-like membrane-anchored regulatory proteins, respectively, which play a crucial role in sensing envelope stress and transferring the information to the cognate HKs. Accordingly, BceS- and LiaS-like IM-HKs do not function as sensor proteins, but rather as signal transfer relays between the sensor and the cognate response regulators read more ...