@article{FoertschHuppMaetal.2011,
  author    = {F{\"o}rtsch, Christina and Hupp, Sabrina and Ma, Jiangtao and Mitchell, Timothy J. and Maier, Elke and Benz, Roland and Iliev, Asparouh I.},
  title     = {Changes in Astrocyte Shape Induced by Sublytic Concentrations of the Cholesterol-Dependent Cytolysin Pneumolysin Still Require Pore-Forming Capacity},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-69084},
  year      = {2011},
  abstract  = {Streptococcus pneumoniae is a common pathogen that causes various infections, such as sepsis and meningitis. A major pathogenic factor of S. pneumoniae is the cholesterol-dependent cytolysin, pneumolysin. It produces cell lysis at high concentrations and apoptosis at lower concentrations. We have shown that sublytic amounts of pneumolysin induce small GTPase-dependent actin cytoskeleton reorganization and microtubule stabilization in human neuroblastoma cells that are manifested by cell retraction and changes in cell shape. In this study, we utilized a live imaging approach to analyze the role of pneumolysin's pore-forming capacity in the actin-dependent cell shape changes in primary astrocytes. After the initial challenge with the wild-type toxin, a permeabilized cell population was rapidly established within 20-40 minutes. After the initial rapid permeabilization, the size of the permeabilized population remained unchanged and reached a plateau. Thus, we analyzed the non-permeabilized (non-lytic) population, which demonstrated retraction and shape changes that were inhibited by actin depolymerization. Despite the non-lytic nature of pneumolysin treatment, the toxin's lytic capacity remained critical for the initiation of cell shape changes. The non-lytic pneumolysin mutants W433F-pneumolysin and delta6-pneumolysin, which bind the cell membrane with affinities similar to that of the wild-type toxin, were not able to induce shape changes. The initiation of cell shape changes and cell retraction by the wild-type toxin were independent of calcium and sodium influx and membrane depolarization, which are known to occur following cellular challenge and suggested to result from the ion channel-like properties of the pneumolysin pores. Excluding the major pore-related phenomena as the initiation mechanism of cell shape changes, the existence of a more complex relationship between the pore-forming capacity of pneumolysin and the actin cytoskeleton reorganization is suggested.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{WippelFoertschHuppetal.2011,
  author    = {Wippel, Carolin and F{\"o}rtsch, Christina and Hupp, Sabrina and Maier, Elke and Benz, Roland and Ma, Jiangtao and Mitchell, Timothy J and Iliev, Asparouh I},
  title     = {Extracellular Calcium Reduction Strongly Increases the Lytic Capacity of Pneumolysin From Streptococcus Pneumoniae in Brain Tissue},
  series = {The Journal of Infectious Diseases},
  volume    = {204},
  journal   = {The Journal of Infectious Diseases},
  number    = {6},
  doi       = {10.1093/infdis/jir434},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-139356},
  pages     = {930-936},
  year      = {2011},
  abstract  = {Background Streptococcus pneumoniae causes serious diseases such as pneumonia and meningitis. Its major pathogenic factor is the cholesterol-dependent cytolysin pneumolysin, which produces lytic pores at high concentrations. At low concentrations, it has other effects, including induction of apoptosis. Many cellular effects of pneumolysin appear to be calcium dependent. Methods  Live imaging of primary mouse astroglia exposed to sublytic amounts of pneumolysin at various concentrations of extracellular calcium was used to measure changes in cellular permeability (as judged by lactate dehydrogenase release and propidium iodide chromatin staining). Individual pore properties were analyzed by conductance across artificial lipid bilayer. Tissue toxicity was studied in continuously oxygenated acute brain slices. Results  The reduction of extracellular calcium increased the lytic capacity of the toxin due to increased membrane binding. Reduction of calcium did not influence the conductance properties of individual toxin pores. In acute cortical brain slices, the reduction of extracellular calcium from 2 to 1 mM conferred lytic activity to pathophysiologically relevant nonlytic concentrations of pneumolysin. Conclusions  Reduction of extracellular calcium strongly enhanced the lytic capacity of pneumolysin due to increased membrane binding. Thus, extracellular calcium concentration should be considered as a factor of primary importance for the course of pneumococcal meningitis. "},
  language  = {en}
}
@article{AngelikaRolandoBeitzingeretal.2011,
  author    = {Angelika, Kronhardt and Rolando, Monica and Beitzinger, Christoph and Stefani, Caroline and Leuber, Michael and Flatau, Gilles and Popoff, Michel R. and Benz, Roland and Lemichez, Emmanuel},
  title     = {Cross-Reactivity of Anthrax and C2 Toxin: Protective Antigen Promotes the Uptake of Botulinum C2I Toxin into Human Endothelial Cells},
  series = {PLoS ONE},
  volume    = {6},
  journal   = {PLoS ONE},
  number    = {8},
  doi       = {10.1371/journal.pone.0023133},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-134791},
  pages     = {e23133},
  year      = {2011},
  abstract  = {Binary toxins are among the most potent bacterial protein toxins performing a cooperative mode of translocation and exhibit fatal enzymatic activities in eukaryotic cells. Anthrax and C2 toxin are the most prominent examples for the AB(7/8) type of toxins. The B subunits bind both host cell receptors and the enzymatic A polypeptides to trigger their internalization and translocation into the host cell cytosol. C2 toxin is composed of an actin ADP-ribosyltransferase (C2I) and C2II binding subunits. Anthrax toxin is composed of adenylate cyclase (EF) and MAPKK protease (LF) enzymatic components associated to protective antigen (PA) binding subunit. The binding and translocation components anthrax protective antigen (PA(63)) and C2II of C2 toxin share a sequence homology of about 35\%, suggesting that they might substitute for each other. Here we show by conducting in vitro measurements that PA(63) binds C2I and that C2II can bind both EF and LF. Anthrax edema factor (EF) and lethal factor (LF) have higher affinities to bind to channels formed by C2II than C2 toxin's C2I binds to anthrax protective antigen (PA(63)). Furthermore, we could demonstrate that PA in high concentration has the ability to transport the enzymatic moiety C2I into target cells, causing actin modification and cell rounding. In contrast, C2II does not show significant capacity to promote cell intoxication by EF and LF. Together, our data unveiled the remarkable flexibility of PA in promoting C2I heterologous polypeptide translocation into cells.},
  language  = {de}
}
@article{TheinBondeBunikisetal.2012,
  author    = {Thein, Marcus and Bonde, Mari and Bunikis, Ignas and Denker, Katrin and Sickmann, Albert and Bergstr{\"o}m, Sven and Benz, Roland},
  title     = {DipA, a Pore-Forming Protein in the Outer Membrane of Lyme Disease Spirochetes Exhibits Specificity for the Permeation of Dicarboxylates},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-75809},
  year      = {2012},
  abstract  = {Lyme disease Borreliae are highly dependent on the uptake of nutrients provided by their hosts. Our study describes the identification of a 36 kDa protein that functions as putative dicarboxylate-specific porin in the outer membrane of Lyme disease Borrelia. The protein was purified by hydroxyapatite chromatography from Borrelia burgdorferi B31 and designated as DipA, for dicarboxylate-specific porin A. DipA was partially sequenced, and corresponding genes were identified in the genomes of B. burgdorferi B31, Borrelia garinii PBi and Borrelia afzelii PKo. DipA exhibits high homology to the Oms38 porins of relapsing fever Borreliae. B. burgdorferi DipA was characterized using the black lipid bilayer assay. The protein has a singlechannel conductance of 50 pS in 1 M KCl, is slightly selective for anions with a permeability ratio for cations over anions of 0.57 in KCl and is not voltage-dependent. The channel could be partly blocked by different di- and tricarboxylic anions. Particular high stability constants up to about 28,000 l/mol (in 0.1 M KCl) were obtained among the 11 tested anions for oxaloacetate, 2-oxoglutarate and citrate. The results imply that DipA forms a porin specific for dicarboxylates which may play an important role for the uptake of specific nutrients in different Borrelia species.},
  subject      = {Medizin},
  language  = {en}
}
@article{BeitzingerStefaniKronhardtetal.2012,
  author    = {Beitzinger, Christoph and Stefani, Caroline and Kronhardt, Angelika and Rolando, Monica and Flatau, Gilles and Lemichez, Emanuel and Benz, Roland},
  title     = {Role of N-Terminal His6-Tags in Binding and Efficient Translocation of Polypeptides into Cells Using Anthrax Protective Antigen (PA)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-76325},
  year      = {2012},
  abstract  = {It is of interest to define bacterial toxin biochemical properties to use them as molecular-syringe devices in order to deliver enzymatic activities into host cells. Binary toxins of the AB7/8-type are among the most potent and specialized bacterial protein toxins. The B subunits oligomerize to form a pore that binds with high affinity host cell receptors and the enzymatic A subunit. This allows the endocytosis of the complex and subsequent injection of the A subunit into the cytosol of the host cells. Here we report that the addition of an N-terminal His6-tag to different proteins increased their binding affinity to the protective antigen (PA) PA63-channels, irrespective if they are related (C2I) or unrelated (gpJ, EDIN) to the AB7/8-family of toxins. His6-EDIN exhibited voltage-dependent increase of the stability constant for binding by a factor of about 25 when the trans-side corresponding to the cell interior was set to 270 mV. Surprisingly, the C. botulinum toxin C2II-channel did not share this feature of PA63. Cell-based experiments demonstrated that addition of an N-terminal His6-tag promoted also intoxication of endothelial cells by C2I or EDIN via PA63. Our results revealed that addition of His6-tags to several factors increase their binding properties to PA63 and enhance the property to intoxicate cells.},
  subject      = {Biologie},
  language  = {en}
}
@article{AistleitnerHeinzHoermannetal.2013,
  author    = {Aistleitner, Karin and Heinz, Christian and Hoermann, Alexandra and Heinz, Eva and Montanaro, Jacqueline and Schulz, Frederik and Maier, Elke and Pichler, Peter and Benz, Roland and Horn, Matthias},
  title     = {Identification and Characterization of a Novel Porin Family Highlights a Major Difference in the Outer Membrane of Chlamydial Symbionts and Pathogens},
  series = {PLoS ONE},
  volume    = {8},
  journal   = {PLoS ONE},
  number    = {1},
  doi       = {10.1371/journal.pone.0055010},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-131176},
  pages     = {e55010},
  year      = {2013},
  abstract  = {The Chlamydiae constitute an evolutionary well separated group of intracellular bacteria comprising important pathogens of humans as well as symbionts of protozoa. The amoeba symbiont Protochlamydia amoebophila lacks a homologue of the most abundant outer membrane protein of the Chlamydiaceae, the major outer membrane protein MOMP, highlighting a major difference between environmental chlamydiae and their pathogenic counterparts. We recently identified a novel family of putative porins encoded in the genome of P. amoebophila by in silico analysis. Two of these Protochlamydia outer membrane proteins, PomS (pc1489) and PomT (pc1077), are highly abundant in outer membrane preparations of this organism. Here we show that all four members of this putative porin family are toxic when expressed in the heterologous host Escherichia coli. Immunofluorescence analysis using antibodies against heterologously expressed PomT and PomS purified directly from elementary bodies, respectively, demonstrated the location of both proteins in the outer membrane of P. amoebophila. The location of the most abundant protein PomS was further confirmed by immuno-transmission electron microscopy. We could show that pomS is transcribed, and the corresponding protein is present in the outer membrane throughout the complete developmental cycle, suggesting an essential role for P. amoebophila. Lipid bilayer measurements demonstrated that PomS functions as a porin with anion-selectivity and a pore size similar to the Chlamydiaceae MOMP. Taken together, our results suggest that PomS, possibly in concert with PomT and other members of this porin family, is the functional equivalent of MOMP in P. amoebophila. This work contributes to our understanding of the adaptations of symbiotic and pathogenic chlamydiae to their different eukaryotic hosts.},
  language  = {en}
}
@article{BeitzingerBronnhuberDuschaetal.2013,
  author    = {Beitzinger, Christoph and Bronnhuber, Annika and Duscha, Kerstin and Riedl, Zsuzsanna and Huber-Lang, Markus and Benz, Roland and Hajos, Gy{\"o}rgy and Barth, Holger},
  title     = {Designed Azolopyridinium Salts Block Protective Antigen Pores In Vitro and Protect Cells from Anthrax Toxin},
  series = {PLoS ONE},
  volume    = {8},
  journal   = {PLoS ONE},
  number    = {6},
  doi       = {10.1371/journal.pone.0066099},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-130097},
  pages     = {e66099},
  year      = {2013},
  abstract  = {Background Several intracellular acting bacterial protein toxins of the AB-type, which are known to enter cells by endocytosis, are shown to produce channels. This holds true for protective antigen (PA), the binding component of the tripartite anthrax-toxin of Bacillus anthracis. Evidence has been presented that translocation of the enzymatic components of anthrax-toxin across the endosomal membrane of target cells and channel formation by the heptameric/octameric \(PA_{63}\) binding/translocation component are related phenomena. Chloroquine and some 4-aminoquinolones, known as potent drugs against Plasmodium falciparium infection of humans, block efficiently the \(PA_{63}\)-channel in a dose dependent way. Methodology/Principal Findings Here we demonstrate that related positively charged heterocyclic azolopyridinium salts block the \(PA_{63}\)-channel in the µM range, when both, inhibitor and \(PA_{63}\) are added to the same side of the membrane, the cis-side, which corresponds to the lumen of acidified endosomal vesicles of target cells. Noise-analysis allowed the study of the kinetics of the plug formation by the heterocycles. In vivo experiments using J774A.1 macrophages demonstrated that the inhibitors of \(PA_{63}\)-channel function also efficiently block intoxication of the cells by the combination lethal factor and \(PA_{63}\) in the same concentration range as they block the channels in vitro. Conclusions/Significance These results strongly argue in favor of a transport of lethal factor through the \(PA_{63}\)-channel and suggest that the heterocycles used in this study could represent attractive candidates for development of novel therapeutic strategies against anthrax.},
  language  = {en}
}
@article{BarcenaUribarriTheinMaieretal.2013,
  author    = {B{\´a}rcena-Uribarri, Iv{\´a}n and Thein, Marcus and Maier, Elke and Bonde, Mari and Bergstr{\"o}m, Sven and Benz, Roland},
  title     = {Use of Nonelectrolytes Reveals the Channel Size and Oligomeric Constitution of the Borrelia burgdorferi P66 Porin},
  series = {PLoS ONE},
  volume    = {8},
  journal   = {PLoS ONE},
  number    = {11},
  doi       = {10.1371/journal.pone.0078272},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-129965},
  pages     = {e78272},
  year      = {2013},
  abstract  = {In the Lyme disease spirochete Borrelia burgdorferi, the outer membrane protein P66 is capable of pore formation with an atypical high single-channel conductance of 11 nS in 1 M KCl, which suggested that it could have a larger diameter than 'normal' Gram-negative bacterial porins. We studied the diameter of the P66 channel by analyzing its single-channel conductance in black lipid bilayers in the presence of different nonelectrolytes with known hydrodynamic radii. We calculated the filling of the channel with these nonelectrolytes and the results suggested that nonelectrolytes (NEs) with hydrodynamic radii of 0.34 nm or smaller pass through the pore, whereas neutral molecules with greater radii only partially filled the channel or were not able to enter it at all. The diameter of the entrance of the P66 channel was determined to be \(\leq\)1.9 nm and the channel has a central constriction of about 0.8 nm. The size of the channel appeared to be symmetrical as judged from one-sidedness of addition of NEs. Furthermore, the P66-induced membrane conductance could be blocked by 80-90\% by the addition of the nonelectrolytes PEG 400, PEG 600 and maltohexaose to the aqueous phase in the low millimolar range. The analysis of the power density spectra of ion current through P66 after blockage with these NEs revealed no chemical reaction responsible for channel block. Interestingly, the blockage of the single-channel conductance of P66 by these NEs occurred in about eight subconductance states, indicating that the P66 channel could be an oligomer of about eight individual channels. The organization of P66 as a possible octamer was confirmed by Blue Native PAGE and immunoblot analysis, which both demonstrated that P66 forms a complex with a mass of approximately 460 kDa. Two dimension SDS PAGE revealed that P66 is the only polypeptide in the complex.},
  language  = {en}
}
@article{AbdaliBarthNorouzyetal.2013,
  author    = {Abdali, Narges and Barth, Enrico and Norouzy, Amir and Schulz, Robert and Nau, Werner M. and Kleinekathofer, Ulrich and Tauch, Andreas and Benz, Roland},
  title     = {Corynebacterium jeikeium jk0268 Constitutes for the 40 Amino Acid Long PorACj, Which Forms a Homooligomeric and Anion- Selective Cell Wall Channel},
  series = {PLoS ONE},
  volume    = {8},
  journal   = {PLoS ONE},
  number    = {10},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-129989},
  pages     = {e75651},
  year      = {2013},
  abstract  = {Corynebacterium jeikeium, a resident of human skin, is often associated with multidrug resistant nosocomial infections in immunodepressed patients. C. jeikeium K411 belongs to mycolic acid-containing actinomycetes, the mycolata and contains a channel-forming protein as judged from reconstitution experiments with artificial lipid bilayer experiments. The channel-forming protein was present in detergent treated cell walls and in extracts of whole cells using organic solvents. A gene coding for a 40 amino acid long polypeptide possibly responsible for the pore-forming activity was identified in the known genome of C. jeikeium by its similar chromosomal localization to known porH and porA genes of other Corynebacterium strains. The gene jk0268 was expressed in a porin deficient Corynebacterium glutamicum strain. For purification temporarily histidine-tailed or with a GST-tag at the N-terminus, the homogeneous protein caused channel-forming activity with an average conductance of 1.25 nS in 1M KCl identical to the channels formed by the detergent extracts. Zero-current membrane potential measurements of the voltage dependent channel implied selectivity for anions. This preference is according to single-channel analysis caused by some excess of cationic charges located in the channel lumen formed by oligomeric alpha-helical wheels. The channel has a suggested diameter of 1.4 nm as judged from the permeability of different sized hydrated anions using the Renkin correction factor. Surprisingly, the genome of C. jeikeium contained only one gene coding for a cell wall channel of the PorA/PorH type found in other Corynebacterium species. The possible evolutionary relationship between the heterooligomeric channels formed by certain Corynebacterium strains and the homooligomeric pore of C. jeikeium is discussed.},
  language  = {en}
}
@article{BenzMaierBaueretal.2014,
  author    = {Benz, Roland and Maier, Elke and Bauer, Susanne and Ludwig, Albrecht},
  title     = {The Deletion of Several Amino Acid Stretches of Escherichia coli Alpha-Hemolysin (HlyA) Suggests That the Channel-Forming Domain Contains Beta-Strands},
  series = {PLOS ONE},
  volume    = {9},
  journal   = {PLOS ONE},
  number    = {12},
  issn      = {1932-6203},
  doi       = {10.1371/journal.pone.0112248},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-118115},
  pages     = {e112248},
  year      = {2014},
  abstract  = {Escherichia coli α-hemolysin (HlyA) is a pore-forming protein of 110 kDa belonging to the family of RTX toxins. A hydrophobic region between the amino acid residues 238 and 410 in the N-terminal half of HlyA has previously been suggested to form hydrophobic and/or amphipathic α-helices and has been shown to be important for hemolytic activity and pore formation in biological and artificial membranes. The structure of the HlyA transmembrane channel is, however, largely unknown. For further investigation of the channel structure, we deleted in HlyA different stretches of amino acids that could form amphipathic β-strands according to secondary structure predictions (residues 71-110, 158-167, 180-203, and 264-286). These deletions resulted in HlyA mutants with strongly reduced hemolytic activity. Lipid bilayer measurements demonstrated that HlyAΔ71-110 and HlyAΔ264-286 formed channels with much smaller single-channel conductance than wildtype HlyA, whereas their channel-forming activity was virtually as high as that of the wildtype toxin. HlyAΔ158-167 and HlyAΔ180-203 were unable to form defined channels in lipid bilayers. Calculations based on the single-channel data indicated that the channels generated by HlyAΔ71-110 and HlyAΔ264-286 had a smaller size (diameter about 1.4 to 1.8 nm) than wildtype HlyA channels (diameter about 2.0 to 2.6 nm), suggesting that in these mutants part of the channel-forming domain was removed. Osmotic protection experiments with erythrocytes confirmed that HlyA, HlyAΔ71-110, and HlyAΔ264-286 form defined transmembrane pores and suggested channel diameters that largely agreed with those estimated from the single-channel data. Taken together, these results suggest that the channel-forming domain of HlyA might contain β-strands, possibly in addition to α-helical structures.},
  language  = {en}
}
@article{BenzJonesYounasetal.2015,
  author    = {Benz, Roland and Jones, Michael D. and Younas, Farhan and Maier, Elke and Modi, Niraj and Mentele, Reinhard and Lottspeich, Friedrich and Kleinekath{\"o}fer, Ulrich and Smit, John},
  title     = {OmpW of Caulobacter crescentus functions as an outer membrane channel for cations},
  series = {PLoS ONE},
  volume    = {10},
  journal   = {PLoS ONE},
  number    = {11},
  doi       = {10.1371/journal.pone.0143557},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-145114},
  pages     = {e0143557},
  year      = {2015},
  abstract  = {Caulobacter crescentus is an oligotrophic bacterium that lives in dilute organic environments such as soil and freshwater. This bacterium represents an interesting model for cellular differentiation and regulation because daughter cells after division have different forms: one is motile while the other is non-motile and can adhere to surfaces. Interestingly, the known genome of C. crescentus does not contain genes predicted to code for outer membrane porins of the OmpF/C general diffusion type present in enteric bacteria or those coding for specific porins selective for classes of substrates. Instead, genes coding for 67 TonB-dependent outer membrane receptors have been identified, suggesting that active transport of specific nutrients may be the norm. Here, we report that high channel-forming activity was observed with crude outer membrane extracts of C. crescentus in lipid bilayer experiments, indicating that the outer membrane of C. crescentus contained an ion-permeable channel with a single-channel conductance of about 120 pS in 1M KCl. The channel-forming protein with an apparent molecular mass of about 20 kDa was purified to homogeneity. Partial protein sequencing of the protein indicated it was a member of the OmpW family of outer membrane proteins from Gram-negative bacteria. This channel was not observed in reconstitution experiments with crude outer membrane extracts of an OmpW deficient C. crescentus mutant. Biophysical analysis of the C. crescentus OmpW suggested that it has features that are special for general diffusion porins of Gram-negative outer membranes because it was not a wide aqueous channel. Furthermore, OmpW of C. crescentus seems to be different to known OmpW porins and has a preference for ions, in particular cations. A putative model for OmpW of C. crescentus was built on the basis of the known 3D-structures of OmpW of Escherichia coli and OprG of Pseudomonas aeruginosa using homology modeling. A comparison of the two known structures with the model of OmpW of C. crescentus suggested that it has a more hydrophilic interior and possibly a larger diameter.},
  language  = {en}
}
@article{KronhardtBeitzingerBarthetal.2016,
  author    = {Kronhardt, Angelika and Beitzinger, Christoph and Barth, Holger and Benz, Roland},
  title     = {Chloroquine Analog Interaction with C2-and Iota-Toxin in Vitro and in Living Cells},
  series = {Toxins},
  volume    = {8},
  journal   = {Toxins},
  number    = {8},
  doi       = {10.3390/toxins8080237},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-168286},
  pages     = {237},
  year      = {2016},
  abstract  = {C2-toxin from Clostridium botulinum and Iota-toxin from Clostridium perfringens belong both to the binary A-B-type of toxins consisting of two separately secreted components, an enzymatic subunit A and a binding component B that facilitates the entry of the corresponding enzymatic subunit into the target cells. The enzymatic subunits are in both cases actin ADP-ribosyltransferases that modify R177 of globular actin finally leading to cell death. Following their binding to host cells' receptors and internalization, the two binding components form heptameric channels in endosomal membranes which mediate the translocation of the enzymatic components Iota a and C2I from endosomes into the cytosol of the target cells. The binding components form ion-permeable channels in artificial and biological membranes. Chloroquine and related 4-aminoquinolines were able to block channel formation in vitro and intoxication of living cells. In this study, we extended our previous work to the use of different chloroquine analogs and demonstrate that positively charged aminoquinolinium salts are able to block channels formed in lipid bilayer membranes by the binding components of C2- and Iota-toxin. Similarly, these molecules protect cultured mammalian cells from intoxication with C2- and Iota-toxin. The aminoquinolinium salts did presumably not interfere with actin ADP-ribosylation or receptor binding but blocked the pores formed by C2IIa and Iota b in living cells and in vitro. The blocking efficiency of pores formed by Iota b and C2IIa by the chloroquine analogs showed interesting differences indicating structural variations between the types of protein-conducting nanochannels formed by Iota b and C2IIa.},
  language  = {en}
}
@article{AbdaliYounasMafakherietal.2018,
  author    = {Abdali, Narges and Younas, Farhan and Mafakheri, Samaneh and Pothula, Karunakar R. and Kleinekath{\"o}fer, Ulrich and Tauch, Andreas and Benz, Roland},
  title     = {Identification and characterization of smallest pore-forming protein in the cell wall of pathogenic Corynebacterium urealyticum DSM 7109},
  series = {BMC Biochemistry},
  volume    = {19},
  journal   = {BMC Biochemistry},
  doi       = {10.1186/s12858-018-0093-9},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226959},
  year      = {2018},
  abstract  = {Background: Corynebacterium urealyticum, a pathogenic, multidrug resistant member of the mycolata, is known as causative agent of urinary tract infections although it is a bacterium of the skin flora. This pathogenic bacterium shares with the mycolata the property of having an unusual cell envelope composition and architecture, typical for the genus Corynebacterium. The cell wall of members of the mycolata contains channel-forming proteins for the uptake of solutes. Results: In this study, we provide novel information on the identification and characterization of a pore-forming protein in the cell wall of C. urealyticum DSM 7109. Detergent extracts of whole C. urealyticum cultures formed in lipid bilayer membranes slightly cation-selective pores with a single-channel conductance of 1.75 nS in 1 M KCl. Experiments with different salts and non-electrolytes suggested that the cell wall pore of C. urealyticum is wide and water-filled and has a diameter of about 1.8 nm. Molecular modelling and dynamics has been performed to obtain a model of the pore. For the search of the gene coding for the cell wall pore of C. urealyticum we looked in the known genome of C. urealyticum for a similar chromosomal localization of the porin gene to known porH and porA genes of other Corynebacterium strains. Three genes are located between the genes coding for GroEL2 and polyphosphate kinase (PKK2). Two of the genes (cur_1714 and cur_1715) were expressed in different constructs in C. glutamicum Delta porA Delta porH and in porin-deficient BL21 DE3 Omp8 E. coli strains. The results suggested that the gene cur_1714 codes alone for the cell wall channel. The cell wall porin of C. urealyticum termed PorACur was purified to homogeneity using different biochemical methods and had an apparent molecular mass of about 4 kDa on tricine-containing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Conclusions: Biophysical characterization of the purified protein (PorACur) suggested indeed that cur_1714 is the gene coding for the pore-forming protein in C. urealyticum because the protein formed in lipid bilayer experiments the same pores as the detergent extract of whole cells. The study is the first report of a cell wall channel in the pathogenic C. urealyticum.},
  language  = {en}
}
@article{KnappBenz2020,
  author    = {Knapp, Oliver and Benz, Roland},
  title     = {Membrane activity and channel formation of the adenylate cyclase toxin (CyaA) of Bordetella pertussis in lipid bilayer membranes},
  series = {Toxins},
  volume    = {12},
  journal   = {Toxins},
  number    = {3},
  issn      = {2072-6651},
  doi       = {10.3390/toxins12030169},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-203362},
  year      = {2020},
  abstract  = {The Gram-negative bacterium Bordetella pertussis is the cause of whooping cough. One of its pathogenicity factors is the adenylate cyclase toxin (CyaA) secreted by a Type I export system. The 1706 amino acid long CyaA (177 kDa) belongs to the continuously increasing family of repeat in toxin (RTX) toxins because it contains in its C-terminal half a high number of nine-residue tandem repeats. The protein exhibits cytotoxic and hemolytic activities that target primarily myeloid phagocytic cells expressing the αMβ2 integrin receptor (CD11b/CD18). CyaA represents an exception among RTX cytolysins because the first 400 amino acids from its N-terminal end possess a calmodulin-activated adenylate cyclase (AC) activity. The entry of the AC into target cells is not dependent on the receptor-mediated endocytosis pathway and penetrates directly across the cytoplasmic membrane of a variety of epithelial and immune effector cells. The hemolytic activity of CyaA is rather low, which may have to do with its rather low induced permeability change of target cells and its low conductance in lipid bilayer membranes. CyaA forms highly cation-selective channels in lipid bilayers that show a strong dependence on aqueous pH. The pore-forming activity of CyaA but not its single channel conductance is highly dependent on Ca\(^{2+}\) concentration with a half saturation constant of about 2 to 4 mM.},
  language  = {en}
}
@article{Benz2020,
  author    = {Benz, Roland},
  title     = {RTX-Toxins},
  series = {Toxins},
  volume    = {12},
  journal   = {Toxins},
  number    = {6},
  issn      = {2072-6651},
  doi       = {10.3390/toxins12060359},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-205860},
  year      = {2020},
  abstract  = {No abstract available.},
  language  = {en}
}
@article{PiselliBenz2021,
  author    = {Piselli, Claudio and Benz, Roland},
  title     = {Fosmidomycin transport through the phosphate-specific porins OprO and OprP of Pseudomonas aeruginosa},
  series = {Molecular Microbiology},
  volume    = {116},
  journal   = {Molecular Microbiology},
  number    = {1},
  doi       = {10.1111/mmi.14693},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-238905},
  pages     = {97 -- 108},
  year      = {2021},
  abstract  = {The Gram-negative bacterium Pseudomonas aeruginosa is an opportunistic pathogen, responsible for many hospital-acquired infections. The bacterium is quite resistant toward many antibiotics, in particular because of the fine-tuned permeability of its outer membrane (OM). General diffusion outer membrane pores are quite rare in this organism. Instead, its OM contains many substrate-specific porins. Their expression is varying according to growth conditions and virulence. Phosphate limitations, as well as pathogenicity factors, result in the induction of the two mono- and polyphosphate-specific porins, OprP and OprO, respectively, together with an inner membrane uptake mechanism and a periplasmic binding protein. These outer membrane channels could serve as outer membrane pathways for the uptake of phosphonates. Among them are not only herbicides, but also potent antibiotics, such as fosfomycin and fosmidomycin. In this study, we investigated the interaction between OprP and OprO and fosmidomycin in detail. We could demonstrate that fosmidomycin is able to bind to the phosphate-specific binding site inside the two porins. The inhibition of chloride conductance of OprP and OprO by fosmidomycin is considerably less than that of phosphate or diphosphate, but it can be measured in titration experiments of chloride conductance and also in single-channel experiments. The results suggest that fosmidomycin transport across the OM of P. aeruginosa occurs through OprP and OprO. Our data with the ones already known in the literature show that phosphonic acid-containing antibiotics are in general good candidates to treat the infections of P. aeruginosa at the very beginning through a favorable OM transport system.},
  language  = {en}
}