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Nature Communications May 2024Members of the Omp85 superfamily of outer membrane proteins (OMPs) found in Gram-negative bacteria, mitochondria and chloroplasts are characterized by a distinctive...
Members of the Omp85 superfamily of outer membrane proteins (OMPs) found in Gram-negative bacteria, mitochondria and chloroplasts are characterized by a distinctive 16-stranded β-barrel transmembrane domain and at least one periplasmic POTRA domain. All previously studied Omp85 proteins promote critical OMP assembly and/or protein translocation reactions. Pseudomonas aeruginosa PlpD is the prototype of an Omp85 protein family that contains an N-terminal patatin-like (PL) domain that is thought to be translocated across the OM by a C-terminal β-barrel domain. Challenging the current dogma, we find that the PlpD PL-domain resides exclusively in the periplasm and, unlike previously studied Omp85 proteins, PlpD forms a homodimer. Remarkably, the PL-domain contains a segment that exhibits unprecedented dynamicity by undergoing transient strand-swapping with the neighboring β-barrel domain. Our results show that the Omp85 superfamily is more structurally diverse than currently believed and suggest that the Omp85 scaffold was utilized during evolution to generate novel functions.
Topics: Pseudomonas aeruginosa; Bacterial Outer Membrane Proteins; Protein Multimerization; Periplasm; Protein Domains; Bacterial Outer Membrane; Models, Molecular; Bacterial Proteins
PubMed: 38782915
DOI: 10.1038/s41467-024-48756-6 -
Journal of Biological Inorganic... Jun 2024Periplasmic nitrate reductase NapA from Campylobacter jejuni (C. jejuni) contains a molybdenum cofactor (Moco) and a 4Fe-4S cluster and catalyzes the reduction of...
Periplasmic nitrate reductase NapA from Campylobacter jejuni (C. jejuni) contains a molybdenum cofactor (Moco) and a 4Fe-4S cluster and catalyzes the reduction of nitrate to nitrite. The reducing equivalent required for the catalysis is transferred from NapC → NapB → NapA. The electron transfer from NapB to NapA occurs through the 4Fe-4S cluster in NapA. C. jejuni NapA has a conserved lysine (K79) between the Mo-cofactor and the 4Fe-4S cluster. K79 forms H-bonding interactions with the 4Fe-4S cluster and connects the latter with the Moco via an H-bonding network. Thus, it is conceivable that K79 could play an important role in the intramolecular electron transfer and the catalytic activity of NapA. In the present study, we show that the mutation of K79 to Ala leads to an almost complete loss of activity, suggesting its role in catalytic activity. The inhibition of C. jejuni NapA by cyanide, thiocyanate, and azide has also been investigated. The inhibition studies indicate that cyanide inhibits NapA in a non-competitive manner, while thiocyanate and azide inhibit NapA in an uncompetitive manner. Neither inhibition mechanism involves direct binding of the inhibitor to the Mo-center. These results have been discussed in the context of the loss of catalytic activity of NapA K79A variant and a possible anion binding site in NapA has been proposed.
Topics: Lysine; Campylobacter jejuni; Nitrate Reductase; Periplasm; Biocatalysis
PubMed: 38782786
DOI: 10.1007/s00775-024-02057-x -
Infection and Immunity Jun 2024causes the genital ulcer disease chancroid and painful cutaneous ulcers in children who live in the tropics. To acquire heme from the host, expresses a TonB-dependent...
causes the genital ulcer disease chancroid and painful cutaneous ulcers in children who live in the tropics. To acquire heme from the host, expresses a TonB-dependent hemoglobin receptor, HgbA, which is necessary and sufficient for to progress to the pustular stage of disease in a controlled human infection model. HgbA transports hemoglobin across the outer membrane; how heme is transported across the cytoplasmic membrane is unclear. In previous studies, transcripts encoding the YfeABCD heme transporter were upregulated in experimental lesions caused by in human volunteers, suggesting the latter may have a role in virulence. Here we constructed a double deletion mutant, 35000HPΔΔ, which exhibited growth defects relative to its parent 35000HP in media containing human hemoglobin as an iron source. Five human volunteers were inoculated at three sites on the skin overlying the deltoid with each strain. The results of the trial showed that papules formed at 100% (95% CI, 71.5, 100) at both 35000HP and 35000HPΔΔ-inoculated sites ( = 1.0). Pustules formed at 60% (95% CI, 25.9, 94.1) at parent-inoculated sites and 53% (95% CI, 18.3, 88.4) at mutant-inoculated sites ( = 0.79). Thus, the ABC transporter encoded by and was dispensable for virulence in humans. In the absence of YfeABCD, likely utilizes other periplasmic binding proteins and ABC-transporters such as HbpA, SapABCDF, and DppBCDF to shuttle heme from the periplasm into the cytoplasm, underscoring the importance of redundancy of such systems in gram-negative pathogens.
Topics: Haemophilus ducreyi; Humans; Chancroid; Bacterial Proteins; Virulence; Iron; Male; Adult; Heme
PubMed: 38780215
DOI: 10.1128/iai.00058-24 -
Nature Communications May 2024Biotic-abiotic hybrid photocatalytic system is an innovative strategy to capture solar energy. Diversifying solar energy conversion products and balancing photoelectron...
Biotic-abiotic hybrid photocatalytic system is an innovative strategy to capture solar energy. Diversifying solar energy conversion products and balancing photoelectron generation and transduction are critical to unravel the potential of hybrid photocatalysis. Here, we harvest solar energy in a dual mode for CuSe nanoparticles biomineralization and seawater desalination by integrating the merits of Shewanella oneidensis MR-1 and biogenic nanoparticles. Photoelectrons generated by extracellular Se nanoparticles power CuSe synthesis through two pathways that either cross the outer membrane to activate periplasmic Cu(II) reduction or are directly delivered into the extracellular space for Cu(I) evolution. Meanwhile, photoelectrons drive periplasmic Cu(II) reduction by reversing MtrABC complexes in S. oneidensis. Moreover, the unique photothermal feature of the as-prepared CuSe nanoparticles, the natural hydrophilicity, and the linking properties of bacterium offer a convenient way to tailor photothermal membranes for solar water production. This study provides a paradigm for balancing the source and sink of photoelectrons and diversifying solar energy conversion products in biotic-abiotic hybrid platforms.
Topics: Solar Energy; Shewanella; Copper; Seawater; Biomineralization; Salinity; Water Purification; Nanoparticles; Catalysis
PubMed: 38778052
DOI: 10.1038/s41467-024-48660-z -
Journal of Nanobiotechnology May 2024The outer membrane vesicles (OMVs) produced by Gram-negative bacteria can modulate the immune system and have great potentials for bacterial vaccine development.
BACKGROUND
The outer membrane vesicles (OMVs) produced by Gram-negative bacteria can modulate the immune system and have great potentials for bacterial vaccine development.
RESULTS
A highly active Acinetobacter baumannii phage lysin, LysP53, can stimulate the production of OMVs after interacting with A. baumannii, Escherichia coli, and Salmonella. The OMVs prepared by the lysin (LOMVs) from A. baumannii showed better homogeneity, higher protein yield, lower endotoxin content, and lower cytotoxicity compared to the naturally produced OMVs (nOMVs). The LOMVs contain a significantly higher number of cytoplasmic and cytoplasmic membrane proteins but a smaller number of periplasmic and extracellular proteins compared to nOMVs. Intramuscular immunization with either LOMVs or nOMVs three times provided robust protection against A. baumannii infections in both pneumonia and bacteremia mouse models. Intranasal immunization offered good protection in the pneumonia model but weaker protection (20-40%) in the bacteremia model. However, with a single immunization, LOMVs demonstrated better protection than the nOMVs in the pneumonia mouse model.
CONCLUSIONS
The novel lysin approach provides a superior choice compared to current methods for OMV production, especially for vaccine development.
Topics: Acinetobacter baumannii; Animals; Acinetobacter Infections; Mice; Bacteriophages; Female; Mice, Inbred BALB C; Bacterial Vaccines; Immunization; Extracellular Vesicles; Bacterial Outer Membrane; Bacterial Outer Membrane Proteins; Disease Models, Animal; Humans; Administration, Intranasal; Viral Proteins
PubMed: 38773507
DOI: 10.1186/s12951-024-02553-x -
The Journal of Biological Chemistry May 2024Disulfide bond formation has a central role in protein folding of both eukaryotes and prokaryotes. In bacteria, disulfide bonds are catalyzed by DsbA and DsbB/VKOR...
Disulfide bond formation has a central role in protein folding of both eukaryotes and prokaryotes. In bacteria, disulfide bonds are catalyzed by DsbA and DsbB/VKOR enzymes. First, DsbA, a periplasmic disulfide oxidoreductase, introduces disulfide bonds into substrate proteins. Then, the membrane enzyme, either DsbB or VKOR, regenerate DsbA's activity by the formation of de novo disulfide bonds which reduce quinone. We have previously performed a high-throughput chemical screen and identified a family of warfarin analogs that target either bacterial DsbB or VKOR. In this work, we expressed functional human VKORc1 in Escherichia coli and performed a structure-activity-relationship analysis to study drug selectivity between bacterial and mammalian enzymes. We found that human VKORc1 can function in E. coli by removing two positive residues, allowing the search for novel anticoagulants using bacteria. We also found one warfarin analog capable of inhibiting both bacterial DsbB and VKOR and a second one antagonized only the mammalian enzymes when expressed in E. coli. The difference in the warfarin structure suggests that substituents at positions three and six in the coumarin ring can provide selectivity between the bacterial and mammalian enzymes. Finally, we identified the two amino acid residues responsible for drug binding. One of these is also essential for de novo disulfide bond formation in both DsbB and VKOR enzymes. Our studies highlight a conserved role of this residue in de novo disulfide-generating enzymes and enable the design of novel anticoagulants or antibacterials using coumarin as a scaffold.
PubMed: 38762182
DOI: 10.1016/j.jbc.2024.107383 -
Proceedings of the National Academy of... May 2024The outer membrane (OM) of didermic gram-negative bacteria is essential for growth, maintenance of cellular integrity, and innate resistance to many antimicrobials. Its...
The outer membrane (OM) of didermic gram-negative bacteria is essential for growth, maintenance of cellular integrity, and innate resistance to many antimicrobials. Its asymmetric lipid distribution, with phospholipids in the inner leaflet and lipopolysaccharides (LPS) in the outer leaflet, is required for these functions. Lpt proteins form a transenvelope bridge that transports newly synthesized LPS from the inner membrane (IM) to OM, but how the bulk of phospholipids are transported between these membranes is poorly understood. Recently, three members of the AsmA-like protein family, TamB, YhdP, and YdbH, were shown to be functionally redundant and were proposed to transport phospholipids between IM and OM in . These proteins belong to the repeating β-groove superfamily, which includes eukaryotic lipid-transfer proteins that mediate phospholipid transport between organelles at contact sites. Here, we show that the IM-anchored YdbH protein interacts with the OM lipoprotein YnbE to form a functional protein bridge between the IM and OM in . Based on AlphaFold-Multimer predictions, genetic data, and in vivo site-directed cross-linking, we propose that YnbE interacts with YdbH through β-strand augmentation to extend the continuous hydrophobic β-groove of YdbH that is thought to shield acyl chains of phospholipids as they travel through the aqueous intermembrane periplasmic compartment. Our data also suggest that the periplasmic protein YdbL prevents extensive amyloid-like multimerization of YnbE in cells. We, therefore, propose that YdbL has a chaperone-like function that prevents uncontrolled runaway multimerization of YnbE to ensure the proper formation of the YdbH-YnbE intermembrane bridge.
Topics: Escherichia coli; Escherichia coli Proteins; Homeostasis; Bacterial Outer Membrane; Bacterial Outer Membrane Proteins; Phospholipids; Lipopolysaccharides; Lipoproteins; Cell Membrane
PubMed: 38748582
DOI: 10.1073/pnas.2321512121 -
Proceedings of the National Academy of... May 2024Cell surface glycans are major drivers of antigenic diversity in bacteria. The biochemistry and molecular biology underpinning their synthesis are important in...
Cell surface glycans are major drivers of antigenic diversity in bacteria. The biochemistry and molecular biology underpinning their synthesis are important in understanding host-pathogen interactions and for vaccine development with emerging chemoenzymatic and glycoengineering approaches. Structural diversity in glycostructures arises from the action of glycosyltransferases (GTs) that use an immense catalog of activated sugar donors to build the repeating unit and modifying enzymes that add further heterogeneity. Classical Leloir GTs incorporate α- or β-linked sugars by inverting or retaining mechanisms, depending on the nucleotide sugar donor. In contrast, the mechanism of known ribofuranosyltransferases is confined to β-linkages, so the existence of α-linked ribofuranose in some glycans dictates an alternative strategy. Here, we use O1 and O2 lipopolysaccharide O antigens as prototypes to describe a widespread, versatile pathway for incorporating side-chain α-linked pentofuranoses by extracytoplasmic postpolymerization glycosylation. The pathway requires a polyprenyl phosphoribose synthase to generate a lipid-linked donor, a MATE-family flippase to transport the donor to the periplasm, and a GT-C type GT (founding the GT136 family) that performs the final glycosylation reaction. The characterized system shares similarities, but also fundamental differences, with both cell wall arabinan biosynthesis in mycobacteria, and periplasmic glucosylation of O antigens first discovered in and . The participation of auxiliary epimerases allows the diversification of incorporated pentofuranoses. The results offer insight into a broad concept in microbial glycobiology and provide prototype systems and bioinformatic guides that facilitate discovery of further examples from diverse species, some in currently unknown glycans.
Topics: Glycosyltransferases; Glycosylation; Citrobacter; O Antigens; Polysaccharides; Bacterial Proteins; Polysaccharides, Bacterial
PubMed: 38748580
DOI: 10.1073/pnas.2402554121 -
BioRxiv : the Preprint Server For... Apr 2024Cell growth in mycobacteria involves cell wall expansion that is restricted to the cell poles. The DivIVA homolog Wag31 is required for this process, but the molecular...
Cell growth in mycobacteria involves cell wall expansion that is restricted to the cell poles. The DivIVA homolog Wag31 is required for this process, but the molecular mechanism and protein partners of Wag31 have not been described. In this study of , we identify a connection between and trehalose monomycolate (TMM) transporter in a suppressor screen, and show that Wag31 and polar regulator PlrA are required for MmpL3's polar localization. In addition, the localization of PlrA and MmpL3 are responsive to nutrient and energy deprivation and inhibition of peptidoglycan metabolism. We show that inhibition of MmpL3 causes delocalized cell wall metabolism, but does not delocalize MmpL3 itself. We found that cells with an MmpL3 C-terminal truncation, which is defective for localization, have only minor defects in polar growth, but are impaired in their ability to downregulate cell wall metabolism under stress. Our work suggests that, in addition to its established function in TMM transport, MmpL3 has a second function in regulating global cell wall metabolism in response to stress. Our data are consistent with a model in which the presence of TMMs in the periplasm stimulates polar elongation, and in which the connection between Wag31, PlrA and the C-terminus of MmpL3 is involved in detecting and responding to stress in order to coordinate synthesis of the different layers of the mycobacterial cell wall in changing conditions.
PubMed: 38746181
DOI: 10.1101/2024.04.29.591792 -
Nature Communications May 2024Microbial Ni homeostasis underpins the virulence of several clinical pathogens. Ni is an essential cofactor in urease and [NiFe]-hydrogenases involved in colonization...
Microbial Ni homeostasis underpins the virulence of several clinical pathogens. Ni is an essential cofactor in urease and [NiFe]-hydrogenases involved in colonization and persistence. Many microbes produce metallophores to sequester metals necessary for their metabolism and starve competing neighboring organisms. The fungal metallophore aspergillomarasmine A (AMA) shows narrow specificity for Zn, Ni, and Co. Here, we show that this specificity allows AMA to block the uptake of Ni and attenuate bacterial Ni-dependent enzymes, offering a potential strategy for reducing virulence. Bacterial exposure to AMA perturbs H metabolism, ureolysis, struvite crystallization, and biofilm formation and shows efficacy in a Galleria mellonella animal infection model. The inhibition of Ni-dependent enzymes was aided by Zn which complexes with AMA and competes with the native nickelophore for the uptake of Ni. Biochemical analyses demonstrated high-affinity binding of AMA-metal complexes to NikA, the periplasmic substrate-binding protein of the Ni uptake system. Structural examination of NikA in complex with Ni-AMA revealed that the coordination geometry of Ni-AMA mimics the native ligand, Ni-(L-His), providing a structural basis for binding AMA-metal complexes. Structure-activity relationship studies of AMA identified regions of the molecule that improve NikA affinity and offer potential routes for further developing this compound as an anti-virulence agent.
Topics: Nickel; Animals; Virulence; Bacterial Proteins; Biofilms; Zinc; Moths; Urease; Biological Transport
PubMed: 38740750
DOI: 10.1038/s41467-024-48232-1