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BioRxiv : the Preprint Server For... Apr 2024Phosphoethanolamine (pEtN) cellulose is a naturally occurring modified cellulose produced by several Enterobacteriaceae. The minimal components of the cellulose...
Phosphoethanolamine (pEtN) cellulose is a naturally occurring modified cellulose produced by several Enterobacteriaceae. The minimal components of the cellulose synthase complex include the catalytically active BcsA enzyme, an associated periplasmic semicircle of hexameric BcsB, as well as the outer membrane (OM)-integrated BcsC subunit containing periplasmic tetratricopeptide repeats (TPR). Additional subunits include BcsG, a membrane-anchored periplasmic pEtN transferase associated with BcsA, and BcsZ, a conserved periplasmic cellulase of unknown biological function. While events underlying the synthesis and translocation of cellulose by BcsA are well described, little is known about its pEtN modification and translocation across the cell envelope. We show that the N-terminal cytosolic domain of BcsA positions three copies of BcsG near the nascent cellulose polymer. Further, the terminal subunit of the BcsB semicircle tethers the N-terminus of a single BcsC protein to establish a trans-envelope secretion system. BcsC's TPR motifs bind a putative cello-oligosaccharide near the entrance to its OM pore. Additionally, we show that only the hydrolytic activity of BcsZ but not the subunit itself is necessary for cellulose secretion, suggesting a secretion mechanism based on enzymatic removal of mislocalized cellulose. Lastly, we introduce pEtN modification of cellulose in orthogonal cellulose biosynthetic systems by protein engineering.
PubMed: 38645035
DOI: 10.1101/2024.04.04.588173 -
Biomolecular NMR Assignments Jun 2024ModA is a soluble periplasmic molybdate-binding protein found in most gram-negative bacteria. It is part of the ABC transporter complex ModABC that moves molybdenum into...
ModA is a soluble periplasmic molybdate-binding protein found in most gram-negative bacteria. It is part of the ABC transporter complex ModABC that moves molybdenum into the cytoplasm, to be used by enzymes that carry out various redox reactions. Since there is no clear analog for ModA in humans, this protein could be a good target for antibacterial drug design. Backbone H, C and N chemical shifts of apo and molybdate-bound ModA from E. coli were assigned at pHs 6.0 and 4.5. In addition, side chain atoms were assigned for apo ModA at pH 6.0. When comparing apo and molybdate-bound ModA at pH 6.0, large chemical shift perturbations are observed, not only in areas near the bound metal, but also in regions that are distant from the metal-binding site. Given the significant conformational change between apo and holo ModA, we might expect the large chemical shift changes to be more widespread; however, since they are limited to specific regions, the residues with large perturbations may reveal allosteric sites that could ultimately be important for the design of antibiotics that target ModA.
Topics: Molybdenum; Nuclear Magnetic Resonance, Biomolecular; Apoproteins; Hydrogen-Ion Concentration; Escherichia coli Proteins; Solutions; Escherichia coli
PubMed: 38642264
DOI: 10.1007/s12104-024-10173-7 -
Environmental Science & Technology Apr 2024Usually, CymA is irreplaceable as the electron transport hub in MR-1 bidirectional electron transfer. In this work, biologically self-assembled FeS nanoparticles...
Usually, CymA is irreplaceable as the electron transport hub in MR-1 bidirectional electron transfer. In this work, biologically self-assembled FeS nanoparticles construct an artificial electron transfer route and implement electron transfer from extracellular into periplasmic space without CymA involvement, which present similar properties to type IV pili. Bacteria are wired up into a network, and more electron transfer conduits are activated by self-assembled transmembrane FeS nanoparticles (electron conduits), thereby substantially enhancing the ammonia production. In this study, we achieved an average NH-N production rate of 391.8 μg·h·L reactor with the selectivity of 98.0% and cathode efficiency of 65.4%. Additionally, the amide group in the protein-like substances located in the outer membrane was first found to be able to transfer electrons from extracellular into intracellular with -type cytochromes. Our work provides a new viewpoint that contributes to a better understanding of the interconnections between semiconductor materials and bacteria and inspires the exploration of new electron transfer chain components.
Topics: Ammonia; Electron Transport; Shewanella; Electrons; Electrodes; Bioelectric Energy Sources
PubMed: 38642050
DOI: 10.1021/acs.est.3c10897 -
Biochemistry May 2024HdeA and HdeB are dimeric ATP-independent acid-stress chaperones, which protect the periplasmic proteins of enteric bacteria at pH 2.0 and 4.0, respectively, during...
HdeA and HdeB are dimeric ATP-independent acid-stress chaperones, which protect the periplasmic proteins of enteric bacteria at pH 2.0 and 4.0, respectively, during their passage through the acidic environment of the mammalian stomach. Despite being structurally similar, they exhibit distinct functional pH optima and conformational prerequisite for their chaperone action. HdeA undergoes a dimer-to-monomer transition at pH 2.0, whereas HdeB remains dimeric at pH 4.0. The monomerization of HdeA exposes its hydrophobic motifs, which facilitates its interaction with the partially folded substrates. How HdeB functions despite maintaining its dimeric conformation has been poorly elucidated in the literature. Herein, we characterized the conformational states and stability of HdeB at its physiologically relevant pH and compared the data with those of HdeA. At pH 4.0, HdeB exhibited distinct spectroscopic signatures and higher stability against heat and guanidine-HCl-induced denaturation than at pH 7.5. We affirm that the pH 4.0 conformer of HdeB was distinct from that at pH 7.5 and that these two conformational states were hierarchically unrelated. Salt-bridge mutations that perturbed HdeB's intersubunit interactions resulted in the loss of its stability and function at pH 4.0. In contrast, mutations affecting intrasubunit interactions enhanced its function, albeit with a reduction in stability. These findings suggest that, unlike HdeA, HdeB acts as a noncanonical chaperone, where pH-dependent stability and conformational rearrangement at pH 4.0 play a core role in its chaperone function rather than its surface hydrophobicity. Such rearrangement establishes a stability-function trade-off that allows HdeB to function while maintaining its stable dimeric state.
Topics: Escherichia coli; Escherichia coli Proteins; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Molecular Chaperones; Protein Conformation; Protein Denaturation; Protein Multimerization; Protein Stability
PubMed: 38640496
DOI: 10.1021/acs.biochem.4c00132 -
Frontiers in Microbiology 2024Defenses against oxidative damage to cell components are essential for survival of bacterial pathogens during infection, and here we have uncovered that the DmsABC...
Defenses against oxidative damage to cell components are essential for survival of bacterial pathogens during infection, and here we have uncovered that the DmsABC S-/N-oxide reductase is essential for virulence and in-host survival of the human-adapted pathogen, . In several different infection models, Δ strains showed reduced immunogenicity as well as lower levels of survival in contact with host cells. Expression of DmsABC was induced in the presence of hypochlorite and paraquat, closely linking this enzyme to defense against host-produced antimicrobials. In addition to methionine sulfoxide, DmsABC converted nicotinamide- and pyrimidine-N-oxide, precursors of NAD and pyrimidine for which is an auxotroph, at physiologically relevant concentrations, suggesting that these compounds could be natural substrates for DmsABC. Our data show that DmsABC forms part of a novel, periplasmic system for defense against host-induced S- and N-oxide stress that also comprises the functionally related MtsZ S-oxide reductase and the MsrAB peptide methionine sulfoxide reductase. All three enzymes are induced following exposure of the bacteria to hypochlorite. MsrAB is required for physical resistance to HOCl and protein repair. In contrast, DmsABC was required for intracellular colonization of host cells and, together with MtsZ, contributed to resistance to N-Chlorotaurine. Our work expands and redefines the physiological role of DmsABC and highlights the importance of different types of S-oxide reductases for bacterial virulence.
PubMed: 38638903
DOI: 10.3389/fmicb.2024.1359513 -
Life Science Alliance Jun 2024The Cag type IV secretion system (Cag T4SS) has an important role in the pathogenesis of gastric cancer. The Cag T4SS outer membrane core complex (OMCC) is organized...
The Cag type IV secretion system (Cag T4SS) has an important role in the pathogenesis of gastric cancer. The Cag T4SS outer membrane core complex (OMCC) is organized into three regions: a 14-fold symmetric outer membrane cap (OMC) composed of CagY, CagX, CagT, CagM, and Cag3; a 17-fold symmetric periplasmic ring (PR) composed of CagY and CagX; and a stalk with unknown composition. We investigated how CagT, CagM, and a conserved antenna projection (AP) region of CagY contribute to the structural organization of the OMCC. Single-particle cryo-EM analyses showed that complexes purified from Δ or Δ mutants no longer had organized OMCs, but the PRs remained structured. OMCCs purified from a CagY antenna projection mutant (CagYAP) were structurally similar to WT OMCCs, except for the absence of the α-helical antenna projection. These results indicate that CagY and CagX are sufficient for maintaining a stable PR, but the organization of the OMC requires CagY, CagX, CagM, and CagT. Our results highlight an unexpected structural independence of two major subdomains of the Cag T4SS OMCC.
Topics: Helicobacter pylori; Type IV Secretion Systems; Periplasm
PubMed: 38631913
DOI: 10.26508/lsa.202302560 -
Journal of Inorganic Biochemistry Jul 2024Cytochrome c nitrite reductase, NrfA, is a soluble, periplasmic pentaheme cytochrome responsible for the reduction of nitrite to ammonium in the Dissimilatory Nitrate... (Review)
Review
Cytochrome c nitrite reductase, NrfA, is a soluble, periplasmic pentaheme cytochrome responsible for the reduction of nitrite to ammonium in the Dissimilatory Nitrate Reduction to Ammonium (DNRA) pathway, a vital reaction in the global nitrogen cycle. NrfA catalyzes this six-electron and eight-proton reduction of nitrite at a single active site with the help of its quinol oxidase partners. In this review, we summarize the latest progress in elucidating the reaction mechanism of ammonia production, including new findings about the active site architecture of NrfA, as well as recent results that elucidate electron transfer and storage in the pentaheme scaffold of this enzyme.
Topics: Nitrates; Oxidation-Reduction; Ammonium Compounds; Cytochromes c1; Nitrate Reductases; Catalytic Domain; Electron Transport; Nitrites; Cytochromes a1
PubMed: 38631103
DOI: 10.1016/j.jinorgbio.2024.112542 -
PloS One 2024Lyme disease is the most prevalent vector-borne infectious disease in Europe and the USA. Borrelia burgdorferi, as the causative agent of Lyme disease, is transmitted to...
Lyme disease is the most prevalent vector-borne infectious disease in Europe and the USA. Borrelia burgdorferi, as the causative agent of Lyme disease, is transmitted to the mammalian host during the tick blood meal. To adapt to the different encountered environments, Borrelia has adjusted the expression pattern of various, mostly outer surface proteins. The function of most B. burgdorferi outer surface proteins remains unknown. We determined the crystal structure of a previously uncharacterized B. burgdorferi outer surface protein BBK01, known to belong to the paralogous gene family 12 (PFam12) as one of its five members. PFam12 members are shown to be upregulated as the tick starts its blood meal. Structural analysis of BBK01 revealed similarity to the coiled coil domain of structural maintenance of chromosomes (SMC) protein family members, while functional studies indicated that all PFam12 members are non-specific DNA-binding proteins. The residues involved in DNA binding were identified and probed by site-directed mutagenesis. The combination of SMC-like proteins being attached to the outer membrane and exposed to the environment or located in the periplasm, as observed in the case of PFam12 members, and displaying the ability to bind DNA, represents a unique feature previously not observed in bacteria.
Topics: Animals; Borrelia burgdorferi; DNA-Binding Proteins; Lyme Disease; Ticks; Membrane Proteins; DNA; Bacterial Outer Membrane Proteins; Mammals
PubMed: 38626020
DOI: 10.1371/journal.pone.0296127 -
Annual Review of Biochemistry Apr 2024Almost all outer membrane proteins (OMPs) in Gram-negative bacteria contain a β-barrel domain that spans the outer membrane (OM). To reach the OM, OMPs must be... (Review)
Review
Almost all outer membrane proteins (OMPs) in Gram-negative bacteria contain a β-barrel domain that spans the outer membrane (OM). To reach the OM, OMPs must be translocated across the inner membrane by the Sec machinery, transported across the crowded periplasmic space through the assistance of molecular chaperones, and finally assembled (folded and inserted into the OM) by the β-barrel assembly machine. In this review, we discuss how considerable new insights into the contributions of these factors to OMP biogenesis have emerged in recent years through the development of novel experimental, computational, and predictive methods. In addition, we describe recent evidence that molecular machines that were thought to function independently might interact to form dynamic intermembrane supercomplexes. Finally, we discuss new results that suggest that OMPs are inserted primarily near the middle of the cell and packed into supramolecular structures (OMP islands) that are distributed throughout the OM.
PubMed: 38603556
DOI: 10.1146/annurev-biochem-030122-033754 -
Insight into the autoproteolysis mechanism of the RsgI9 anti-σ factor from Clostridium thermocellum.Proteins Apr 2024Clostridium thermocellum is a potential microbial platform to convert abundant plant biomass to biofuels and other renewable chemicals. It efficiently degrades...
Clostridium thermocellum is a potential microbial platform to convert abundant plant biomass to biofuels and other renewable chemicals. It efficiently degrades lignocellulosic biomass using a surface displayed cellulosome, a megadalton sized multienzyme containing complex. The enzymatic composition and architecture of the cellulosome is controlled by several transmembrane biomass-sensing RsgI-type anti-σ factors. Recent studies suggest that these factors transduce signals from the cell surface via a conserved RsgI extracellular (CRE) domain (also called a periplasmic domain) that undergoes autoproteolysis through an incompletely understood mechanism. Here we report the structure of the autoproteolyzed CRE domain from the C. thermocellum RsgI9 anti-σ factor, revealing that the cleaved fragments forming this domain associate to form a stable α/β/α sandwich fold. Based on AlphaFold2 modeling, molecular dynamics simulations, and tandem mass spectrometry, we propose that a conserved Asn-Pro bond in RsgI9 autoproteolyzes via a succinimide intermediate whose formation is promoted by a conserved hydrogen bond network holding the scissile peptide bond in a strained conformation. As other RsgI anti-σ factors share sequence homology to RsgI9, they likely autoproteolyze through a similar mechanism.
PubMed: 38597224
DOI: 10.1002/prot.26690