Cell Envelope Biogenesis and, Molecular Strategies to Maintain Cellular Homeostasis in Bacteria
A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Molecular Microbiology".
Deadline for manuscript submissions: 31 December 2024 | Viewed by 31
Special Issue Editors
Interests: protein folding; heat shock response; peptidyl prolyl cis/trans isomerases; disulfide bond formation; RpoE sigma factor; two-component systems; envelope stress; transcription factors; lipopolysaccharide
Special Issues, Collections and Topics in MDPI journals
Interests: lipopolysaccharide assembly and its modifications: heat shock response; protein folding catalysts; chaperones; proteases; regulatory RNAs; two-component systems, RpoE sigma factor
Special Issues, Collections and Topics in MDPI journals
Special Issue Information
Dear Colleagues,
Gram-negative bacteria are endowed by a unique outer membrane (OM) and an inner membrane separated by the periplasm. The OM is asymmetric in nature due to the presence of a complex glycolipid lipopolysaccharide (LPS) located in the outer leaflet with phospholipids facing the inner leaflet. The maintenance of this asymmetry is crucial for bacterial viability to provide a permeability barrier. Hence, bacteria maintain a tight balance between LPS and phospholipids by regulating a balanced flux of common metabolic precursors to these two essential components of the cell envelope. In this process, the newly identified essential LPS assembly proteins, LapB and LapC, regulate the turnover of the LpxC enzyme, which mediates the first committed step in LPS biosynthesis and plays a critical role in the activity of FtsH protease towards LpxC. However, many questions remain to be answered, such as how LPS is recognized by LapB and LapC and how the amounts of fatty acids are regulated. Furthermore, there is complex regulation of LPS heterogeneity, and its molecular basis is not fully understood. Additionally, substantial gaps exist in our understanding of the pathways of LPS assembly and transport, maturation of outer membrane proteins (OMPs) and their targeting to OM, and transport of phospholipids. The OM is critical for bacterial virulence and is porous in nature, and proteins must rapidly fold in their three-dimensional structure in the periplasm for their function in this compartment, which is devoid of ATP or maintained in a folding competent state for insertion into the OM. To maintain cellular homeostasis in the cell envelope, bacteria have developed signal transduction pathways to respond to defects in protein folding in the periplasm or when the LPS assembly is impaired. These pathways include the induction of extracytoplasmic function sigma factors (ECFs) or specialized two-component systems such as PhoP/Q to induce the expression of genes whose products can act either as chaperones or proteases or participate in LPS assembly. Thus, the protein-coding arms of ECF sigma factor RpoE include catalysts mediating rate-limiting steps of protein folding such as disulfide bond formation or factors involved in the assembly of OMPs and LPS and protein quality control by proteases such as DegP (HtrA). The non-coding arm of such regulators includes a set of regulatory RNAs that repress the synthesis of abundant OM components to keep their amounts in check under stress conditions. Thus, in this Special Issue, some of these integrated pathways and their components that regulate cell envelope homeostasis will be covered.
Prof. Dr. Satish Raina
Dr. Gracjana Klein
Guest Editors
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Keywords
- LpxC and the regulation of LPS
- periplasmic protein folding
- disulfide bond formation
- BAM proteins and assembly of outer membrane proteins
- periplasmic protease DegP (HtrA)
- lipopolysaccharide assembly
- LPS modifications and diversity
- LPS and phospholipid trafficking
- bacterial virulence factors
- antibiotic resistance
- extracytoplasmic function sigma factors
- regulatory RNAs
- two-component systems
- lipid A and its modification
