Journal: Journal of Biological Chemistry

Abbreviation

J Biol Chem

Publisher

American Society for Biochemistry and Molecular Biology

Journal Volumes

ISSN

0021-9258
1083-351X

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Publications 1 - 10 of 320
  • A Peptidomimetic Antibiotic Targets Outer Membrane Proteins and Disrupts Selectively the Outer Membrane in Escherichia coli
    Item type: Journal Article
    Urfer, Matthias; Bogdanovic, Jasmina; Lo Monte, Fabio; et al. (2016)
    Journal of Biological Chemistry
    Increasing antibacterial resistance presents a major challenge in antibiotic discovery. One attractive target in Gram-negative bacteria is the unique asymmetric outer membrane (OM), which acts as a permeability barrier that protects the cell from external stresses, such as the presence of antibiotics. We describe a novel β-hairpin macrocyclic peptide JB-95 with potent antimicrobial activity against Escherichia coli. This peptide exhibits no cellular lytic activity, but electron microscopy and fluorescence studies reveal an ability to selectively disrupt the OM but not the inner membrane of E. coli. The selective targeting of the OM probably occurs through interactions of JB-95 with selected β-barrel OM proteins, including BamA and LptD as shown by photolabeling experiments. Membrane proteomic studies reveal rapid depletion of many β-barrel OM proteins from JB-95-treated E. coli, consistent with induction of a membrane stress response and/or direct inhibition of the Bam folding machine. The results suggest that lethal disruption of the OM by JB-95 occurs through a novel mechanism of action at key interaction sites within clusters of β-barrel proteins in the OM. These findings open new avenues for developing antibiotics that specifically target β-barrel proteins and the integrity of the Gram-negative OM.
  • Distinct Roles of Secreted HtrA Proteases from Gram-negative Pathogens in Cleaving the Junctional Protein and Tumor Suppressor E-cadherin
    Item type: Journal Article
    Hoy, Benjamin; Geppert, Tim; Boehm, Manja; et al. (2012)
    Journal of Biological Chemistry
    The periplasmic chaperone and serine protease HtrA is important for bacterial stress responses and protein quality control. Recently, we discovered that HtrA from Helicobacter pylori is secreted and cleaves E-cadherin to disrupt the epithelial barrier, but it remained unknown whether this maybe a general virulence mechanism. Here, we show that important other pathogens including enteropathogenic Escherichia coli, Shigella flexneri, and Campylobacter jejuni, but not Neisseria gonorrhoeae, cleaved E-cadherin on host cells. HtrA deletion in C. jejuni led to severe defects in E-cadherin cleavage, loss of cell adherence, paracellular transmigration, and basolateral invasion. Computational modeling of HtrAs revealed a conserved pocket in the active center exhibiting pronounced proteolytic activity. Differential E-cadherin cleavage was determined by an alanine-to-glutamine exchange in the active center of neisserial HtrA. These data suggest that HtrA-mediated E-cadherin cleavage is a prevalent pathogenic mechanism of multiple Gram-negative bacteria representing an attractive novel target for therapeutic intervention to combat bacterial infections.
  • Expression, Purification, and Characterization of Isoform 1 of the Plasma Membrane Ca²⁺ Pump
    Item type: Journal Article
    Guerini, Danilo; Pan, Bin; Crivelli, Ernesto (2003)
    Journal of Biological Chemistry
    The plasma membrane Ca²⁺ ATPase isoform 1(PMCA1) is ubiquitously distributed in tissues and cells, but only scarce information is available on its properties. The isoform was overexpressed in Sf9 cells, purified on calmodulin columns, and characterized functionally. The level of expression was very low, but sufficient amounts of the protein could be isolated for biochemical characterization. The affinity of PMCA1 for calmodulin was similar to that of PMCA4, the other ubiquitous PMCA isoform. The affinity of PMCA1 for ATP, evaluated by the formation of the phosphorylated intermediate, was higher than that of the PMCA4 pump. The recombinant PMCA1 pump was a much better substrate for the cAMP-dependent protein kinase than the PMCA2 and PMCA4 isoforms. Pulse and chase experiments on Sf9 cells overexpressing the PMCA pumps showed that PMCA1 was much less stable than the PMCA4 and PMCA2 isoforms, i.e. PMCA1 had a much higher sensitivity to degradation by calpain. The effect of calpain was not the result of a general higher susceptibility of the PMCA1 to proteolytic degradation, because the pattern of degradation by trypsin was the same in the three isoforms.
  • Effects of Protein and Gene Transfer of the Angiopoietin-1 Fibrinogen-like Receptor-binding Domain on Endothelial and Vessel Organization
    Item type: Journal Article
    Weber, Cornelia C.; Cai, Hao; Ehrbar, Martin; et al. (2005)
    Journal of Biological Chemistry
    The vessel-stabilizing effect of angiopoietin-1 (Ang1)/Tie2 receptor signaling is a potential target for pro-angiogenic therapies as well as anti-angiogenic inhibition of tumor growth. We explored the endothelial and vascular specific activities of the Ang1 monomer, i.e. dissociated from its state as an oligomer. A truncated monomeric Ang1 variant (i.e. ΔAng1) containing the isolated fibrinogen-like receptor-binding domain of Ang1 was created and recombinantly produced in insect cells. ΔAng1 ligated the Tie2 receptor without triggering its phosphorylation. Moreover, monomeric ΔAng1 was observed to bind α₅β₁ integrin with similar affinity compared with Tie2. Unexpectedly, in vitro treatment of endothelial cells with ΔAng1 showed some of the known effects of full-length Ang1, including inhibition of basal endothelial cell permeability and stimulation of cell adhesion as well as activation of MAPKs. Local treatment of the microvasculature of the developing chicken chorioallantoic membrane with the ΔAng1 protein led to profound reduction of the mean vascular length density, thinning of vessels, and reduction of the number of vessel branching points. Similar effects were observed in side-by-side experiments with the recombinant full-length Ang1 protein. These effects of simplification of the vessel branching pattern were confirmed through local gene transfer with lentiviral particles encoding ΔAng1 or full-length Ang1. Together, our findings suggest a potential use for exogenous Ang1 in reducing rather than increasing vascular density. Furthermore, we show that the isolated receptor-binding domain of Ang1 is capable of mediating some effects of full-length Ang1 independently of Tie2 phosphorylation, possibly through integrin ligation.
  • NMR investigation of structures of G-protein coupled receptor folding intermediates
    Item type: Journal Article
    Poms, Martin; Ansorge, Philipp; Martinez-Gil, Luis; et al. (2016)
    Journal of Biological Chemistry
  • Deletion of the Protein Kinase A/Protein Kinase G Target SMTNL1 Promotes an Exercise-adapted Phenotype in Vascular Smooth Muscle
    Item type: Journal Article
    Wooldridge, Anne A.; Fortner, Christopher N.; Lontay, Beata; et al. (2008)
    Journal of Biological Chemistry
  • FANCD2-associated Nuclease 1, but Not Exonuclease 1 or Flap Endonuclease 1, Is Able to Unhook DNA Interstrand Cross-links in Vitro
    Item type: Journal Article
    Pizzolato, Julia; Mukherjee, Shivam; Schärer, Orlando D.; et al. (2015)
    Journal of Biological Chemistry
    Cisplatin and its derivatives, nitrogen mustards and mitomycin C, are used widely in cancer chemotherapy. Their efficacy is linked primarily to their ability to generate DNA interstrand cross-links (ICLs), which effectively block the progression of transcription and replication machineries. Release of this block, referred to as unhooking, has been postulated to require endonucleases that incise one strand of the duplex on either side of the ICL. Here we investigated how the 5′ flap nucleases FANCD2-associated nuclease 1 (FAN1), exonuclease 1 (EXO1), and flap endonuclease 1 (FEN1) process a substrate reminiscent of a replication fork arrested at an ICL. We now show that EXO1 and FEN1 cleaved the substrate at the boundary between the single-stranded 5′ flap and the duplex, whereas FAN1 incised it three to four nucleotides in the double-stranded region. This affected the outcome of processing of a substrate containing a nitrogen mustard-like ICL two nucleotides in the duplex region because FAN1, unlike EXO1 and FEN1, incised the substrate predominantly beyond the ICL and, therefore, failed to release the 5′ flap. We also show that FAN1 was able to degrade a linear ICL substrate. This ability of FAN1 to traverse ICLs in DNA could help to elucidate its biological function, which is currently unknown.
  • Influence of pH on NMR structure and stability of the human prion protein globular domain
    Item type: Journal Article
    Calzolai, Luigi; Zahn, Ralph (2003)
    Journal of Biological Chemistry
  • Three-dimensional Structure of the Barley β-d-Glucan Glucohydrolase in Complex with a Transition State Mimic
    Item type: Journal Article
    Hrmova, Maria; Gori, Ross De; Smith, Brian J.; et al. (2004)
    Journal of Biological Chemistry
  • Fructose Protects Murine Hepatocytes from Tumor Necrosis Factor-induced Apoptosis by Modulating JNK Signaling
    Item type: Journal Article
    Speicher, Tobias; Köhler, Ulrike A.; Chouker, Alexander; et al. (2012)
    Journal of Biological Chemistry
    Fructose-induced hepatic ATP depletion prevents TNF-induced apoptosis, whereas it contrarily enhances CD95-induced hepatocyte apoptosis in vitro and in vivo. By contrast, transformed liver cells are not protected against TNF due to metabolic alterations, allowing selective tumor targeting. We analyzed the molecular mechanisms by which fructose modulates cytokine-induced apoptosis. A release of adenosine after fructose-induced ATP depletion, followed by a cAMP response, was demonstrated. Likewise, cAMP and adenosine mimicked per se the modulation by fructose of CD95- and TNF-induced apoptosis. The effects of fructose on cytokine-induced apoptosis were sensitive to inhibition of protein kinase A. Fructose prevented the pro-apoptotic, sustained phase of TNF-induced JNK signaling and thereby blocked bid-mediated activation of the intrinsic mitochondrial apoptosis pathway in a PKA-dependent manner. We explain the dichotomal effects of fructose on CD95- and TNF-induced cell death by the selective requirement of JNK signaling for the latter. These findings provide a mechanistic rationale for the protection of hepatocytes from TNF-induced cell death by pharmacological doses of fructose.
Publications 1 - 10 of 320