Structure and Function of the Stressosome Signalling Hub

Abstract

The stressosome is a multi-protein signal integration and transduction hub found in a wide range of bacterial species. The role that the stressosome plays in regulating the transcription of genes involved in the general stress response has been studied most extensively in the Gram-positive model organism Bacillus subtilis. The stressosome receives and relays the signal(s) that initiate a complex phosphorylation-dependent partner switching cascade, resulting in the activation of the alternative sigma factor σ. This sigma factor controls transcription of more than 150 genes involved in the general stress response. X-ray crystal structures of individual components of the stressosome and single-particle cryo-EM reconstructions of stressosome complexes, coupled with biochemical and single cell analyses, have permitted a detailed understanding of the dynamic signalling behaviour that arises from this multi-protein complex. Furthermore, bioinformatics analyses indicate that genetic modules encoding key stressosome proteins are found in a wide range of bacterial species, indicating an evolutionary advantage afforded by stressosome complexes. Interestingly, the genetic modules are associated with a variety of signalling modules encoding secondary messenger regulation systems, as well as classical two-component signal transduction systems, suggesting a diversification in function. In this chapter we review the current research into stressosome systems and discuss the functional implications of the unique structure of these signalling complexes.

Experimental evolution of Bacillus subtilis

“…Motivations for a similar adaptation of B. subtilis are three-fold. First, the topic of cell stress is a significant research front, in which B. subtilis is a commonly used system (Pane-Farre et al, 2017). Second, a B. subtilis strain adapted to high-temperature growth could have practical value for biotechnological applications, potentially reducing energy use and lowering production costs for fermentation, as has been noted for thermophilic platforms (Taylor et al, 2011).…”

Three decades of listeriology through the prism of technological advances

“…Activation of SigB relies on transduction of intestinal signals by bacterial envelope components, such as the membrane miniprotein Prli42, discovered recently through mass spectrometry (MS)‐based proteomics, and a cytoplasmic complex composed of multiple copies of the three proteins RsbR, RsbS and RsbT, the stessosome (Impens et al, ). Studies in Bacillus subtilis showed that the RsbS scaffold protein and RsbR form the core of the stressosome, which is phosphorylated by RsbT upon stress (Pané‐Farré et al, ). Atomic resolution cryo‐electron microscopy (EM) of the RsbR‐RsbS core in Listeria revealed a similar 60‐mers icosahedron organisation and its potential activation by phosphorylation of RsbR (Figure ), providing a refined model of stressosome mechanics and signal transduction, that may extend to other bacteria (Williams et al, ).…”

“…Studies in Bacillus subtilis showed that the RsbS scaffold protein and RsbR form the core of the stressosome, which is phosphorylated by RsbT upon stress (Pané-Farré et al, 2017). Atomic resolution cryoelectron microscopy (EM) of the RsbR-RsbS core in Listeria revealed a similar 60-mers icosahedron organisation and its potential activation F I G U R E 1 Schematic representation of Listeria monocytogenes infection cycle in host cells.…”

Bacillus subtilis, the model Gram‐positive bacterium: 20 years of annotation refinement

“…Three major functions are linked to this situation: overcoming deleterious actions of non‐living and living organisms, escaping to other niches, possibly far away or staying in place. Bacillus subtilis monitors this situation via specific sigma factors (Helmann, 2016) and protein phosphorylation cascades (Schultz, 2016; Pane‐Farre et al ., 2017). These will not be further discussed here (except to note that the concept of stress being very ambiguous, as all living organisms suffer multiple transitions, it should probably be avoided to be replaced by the idea of transition management).…”