Structural and Functional Insights into Bacillus subtilis Sigma Factor Inhibitor, CsfB

Abstract

SummaryGlobal changes in bacterial gene expression can be orchestrated by the coordinated activation/deactivation of alternative sigma (σ) factor subunits of RNA polymerase. Sigma factors themselves are regulated in myriad ways, including via anti-sigma factors. Here, we have determined the solution structure of anti-sigma factor CsfB, responsible for inhibition of two alternative sigma factors, σG and σE, during spore formation by Bacillus subtilis. CsfB assembles into a symmetrical homodimer, with each monomer bound to a single Zn2+ ion via a treble-clef zinc finger fold. Directed mutagenesis indicates that dimer formation is critical for CsfB-mediated inhibition of both σG and σE, and we have characterized these interactions in vitro. This work represents an advance in our understanding of how CsfB mediates inhibition of two alternative sigma factors to drive developmental gene expression in a bacterium.

From Root to Tips: Sporulation Evolution and Specialization inBacillus subtilisand the Intestinal PathogenClostridioides difficile

“…Later in sporulation, CsfB is produced in the mother cell, under the control of σ K and helps preventing protracted activity of σ E , to which it also binds an inhibits (Serrano et al. 2015; Martinez-Lumbreras et al. 2018).…”

The roles of cytosolic quality control proteins, SGTA and the BAG6 complex, in disease

“…SGTA is highly conserved throughout mammals and higher eukaryotes with the TPR domain sharing the greatest similarity across the different species (Martinez-Lumbreras et al, 2018). The N-terminal domain of SGTA forms a tight dimer with a negatively charged patch on its surface which has been shown to bind with positively charged UBL domains from both BAG6 and UBL4A domain through electrostatic interactions (Darby et al, 2014).…”

“…Typically TPR domains (Darby et al, 2014); TPR domain (red) residues 84-210 from PDB: 2VYI (Dutta & Tan, 2008). There is currently no solved structure for the C-terminal domain (blue) which encompasses NNP and Q-rich regions (Martinez-Lumbreras et al, 2018). are made up of between 3 and 16 tandem repeats-SGTA contains 3 repeats with each repeat containing 2 almost identically structured antiparallel folded alpha helices (Dutta & Tan, 2008;Krysztofinska et al, 2017). There is additionally a seventh alpha helix known as the C-terminal capping helix that aligns against the second helix of the third repeat, helix 6.…”

“…This allows for SGTA to bind to and then shield improperly or incompletely folded proteins with exposed hydrophobic regions, and thus provide a vital role within the protein quality control network. Very recently another important motif has been identified in the C-terminus called the NNP motif consisting of three copies of asparagine-asparagineproline (Martinez-Lumbreras et al, 2018). The C-terminal domain has also been found to transiently dimerize, probably around hydrophobic substrates in the manner of a pair of tweezers (Martinez-Lumbreras et al, 2018).…”

First-In-Class Inhibitors Targeting the Interaction between Bacterial RNA Polymerase and Sigma Initiation Factor Affect the Viability and Toxin Release of Streptococcus pneumoniae

“…The interaction between RNAP and σ factors has been considered a target for novel antimicrobial discovery [9,10,11,12,13] as opposed to other inhibitors which target RNAP enzyme activities (such as rifampicin binding near the active site, lipiarmycin leading to allosteric inhibition of template DNA binding, myxopyronin and squaramides blocking the switch region of the RNAP clamp open-close) [5]. Previously, by rational design and pharmacophore model-based in silico screening, we have identified three chemical compounds (Figure 2) that inhibit bacterial RNAP-σ interaction by binding to the CH region of RNAP [14].…”