The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Tapas Biswas - One of the best experts on this subject based on the ideXlab platform.
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Porin of shigella dysenteriae activates mouse peritoneal macrophage through toll like receptors 2 and 6 to induce polarized type i response
Molecular Immunology, 2007Co-Authors: Amlan Biswas, Pallavi Banerjee, Gayatri Mukherjee, Tapas BiswasAbstract:Abstract Porin of Shigella dysenteriae type 1 coexpressed Toll-like receptor (TLR) 2 and TLR6 on peritoneal cavity (PerC) macrophages (MΦ) of C57BL/6 mice implicating that both the TLRs are essential as a combinatorial repertoire to recognize the protein. Besides TLRs, mRNA for MyD88 and TRAF6, and nuclear translocation of NF-κB were enhanced that indicate their involvement in tandem in the activity of Porin. The protein selectively up-regulated CD80 on the activated MΦ together with MHC class II molecule and CD40, and had no effect on CD86 expression. The Porin-induced profile of MIP-1α, MIP-1β and RANTES showed strong bias for chemokines correlated with M1 polarization. Intracellular expression and release of TNF-α and IL-12 in presence of Porin was found to be TLR2 and NF-κB dependent. Induction of TNF-α and IL-12 along with the chemokine profile suggests type I polarization of the MΦ that would influence Th1-type response.
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Porin of shigella dysenteriae enhances mrna levels for toll like receptor 2 and myd88 up regulates cd80 of murine macrophage and induces the release of interleukin 12
Fems Immunology and Medical Microbiology, 2003Co-Authors: Nabendu S Chatterjee, S K Bhattacharya, Tapas BiswasAbstract:Sera of patients convalescing from shigellosis reacted strongly and specifically with the 38,000 Da monomer of Porin of Shigella dysenteriae type 1. Since human, the only natural host of S. dysenteriae type 1, recognized the protein through humoral immune response, it is of great significance to study the surface-exposed outer membrane antigen as an adjuvant. Porin treatment of CD11b+ peritoneal cavity (PerC) MΦ of BALB/c mouse was found to up-regulate CD80 on cell surface and had no effect on CD86 expression. The surface expression of CD80 got increased by 1.6-fold in the presence of gamma interferon (IFN-γ) supporting selective regulation of the B7–1 (CD80) member of the B7 family. MΦ released 7.25 pg of interleukin-12 (IL-12) in the presence of Porin. The protein in combination with IFN-γ augmented profoundly the release of IL-12 by 2.6-fold. Porin-mediated induction of IL-12 release would therefore influence Th1-type response, known to be preferentially triggered due to up-regulation of CD80 expression. Treatment of PerC MΦ by the protein showed an increase of mRNA for both Toll-like receptor (TLR)2 and myeloid differentiation factor 88 (MyD88) by 2- and 2.3-fold respectively, emphasizing that TLR2 is essential for recognition of S. dysenteriae type 1 Porin. Understanding the mechanism of adjuvanticity of Porin of S. dysenteriae type 1 is a necessary step towards the development of a better adjuvant against shigellosis.
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Murine splenocyte proliferation by Porin of Shigella dysenteriae type 1 and inhibition of bacterial invasion of HeLa cell by anti-Porin antibody.
FEMS microbiology letters, 1996Co-Authors: Sudipta Roy, Tapas BiswasAbstract:The purified Porin of Shigella dysenteriae type 1 showed strong mitogenic activity for murine splenocytes. Preincubation of S. dysenteriae type 1 with anti-Porin antibody reduced the bacterial plaque formation in HeLa cell monolayers by 45%. The two immunobiological activities indicate that Porin might be important in the induction of protective immunity against shigellosis.
Vicente J. Benedí - One of the best experts on this subject based on the ideXlab platform.
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energy dependent accumulation of norfloxacin and Porin expression in clinical isolates of klebsiella pneumoniae and relationship to extended spectrum β lactamase production
Antimicrobial Agents and Chemotherapy, 2002Co-Authors: Luis Martinezmartinez, Alvaro Pascual, Isabel Garcia, Providencia Joyanes, Antonio Domenechsanchez, Maria Del Carmen Conejo, Vicente J. BenedíAbstract:The relationships between Porin deficiency, active efflux of fluoroquinolones, and extended-spectrum β-lactamase (ESBL) production were determined for 53 clinical isolates of Klebsiella pneumoniae. Thirty-two ESBL-positive strains (including 22 strains expressing Porins and 10 strains lacking Porins) and 21 ESBL-negative strains were evaluated. Active efflux of norfloxacin was defined as a ≥50% increase in the accumulation of norfloxacin in the presence of carbonyl cyanide m-chlorophenylhydrazone (CCCP) in comparison with the corresponding basal value in the absence of CCCP. The quinolone resistance-determining regions of both gyrA and parC from 13 strains, representing all isolates with different Porin profiles and with or without active efflux, were determined. Porin loss was significantly more common among ESBL-positive strains (10 of 32 [31.2%]) than among ESBL-negative strains (0 of 2 [0%]) (P 0.05). Basal values of norfloxacin accumulation were higher in strains lacking active efflux than in those that had this mechanism (P < 0.05). In the absence of topoisomerase changes, the contribution of either Porin loss or active efflux to fluoroquinolone resistance in K. pneumoniae was negligible. It is concluded that among K. pneumoniae strains of clinical origin, Porin loss was observed only in those producing ESBL, and that a significant number of Porin-deficient strains also expressed active efflux of norfloxacin. In terms of fluoroquinolone resistance, both mechanisms are significant only in the presence of topoisomerase modifications.
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energy dependent accumulation of norfloxacin and Porin expression in clinical isolates of klebsiella pneumoniae and relationship to extended spectrum β lactamase production
Antimicrobial Agents and Chemotherapy, 2002Co-Authors: Luis Martinezmartinez, Alvaro Pascual, M C Conejo, Isabel Garcia, Providencia Joyanes, Antonio Domenechsanchez, Vicente J. BenedíAbstract:The relationships between Porin deficiency, active efflux of fluoroquinolones, and extended-spectrum β-lactamase (ESBL) production were determined for 53 clinical isolates of Klebsiella pneumoniae. Thirty-two ESBL-positive strains (including 22 strains expressing Porins and 10 strains lacking Porins) and 21 ESBL-negative strains were evaluated. Active efflux of norfloxacin was defined as a ≥50% increase in the accumulation of norfloxacin in the presence of carbonyl cyanide m-chlorophenylhydrazone (CCCP) in comparison with the corresponding basal value in the absence of CCCP. The quinolone resistance-determining regions of both gyrA and parC from 13 strains, representing all isolates with different Porin profiles and with or without active efflux, were determined. Porin loss was significantly more common among ESBL-positive strains (10 of 32 [31.2%]) than among ESBL-negative strains (0 of 2 [0%]) (P 0.05). Basal values of norfloxacin accumulation were higher in strains lacking active efflux than in those that had this mechanism (P < 0.05). In the absence of topoisomerase changes, the contribution of either Porin loss or active efflux to fluoroquinolone resistance in K. pneumoniae was negligible. It is concluded that among K. pneumoniae strains of clinical origin, Porin loss was observed only in those producing ESBL, and that a significant number of Porin-deficient strains also expressed active efflux of norfloxacin. In terms of fluoroquinolone resistance, both mechanisms are significant only in the presence of topoisomerase modifications.
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development of resistance during antimicrobial therapy caused by insertion sequence interruption of Porin genes
Antimicrobial Agents and Chemotherapy, 1999Co-Authors: Santiago Hernandezalles, Vicente J. Benedí, Juan M. Tomás, Luis Martinezmartinez, Alvaro Pascual, Alicia Aguilar, Sebastián AlbertíAbstract:We have demonstrated by using an in vitro approach that interruption of the OmpK36 Porin gene by insertion sequences (ISs) is a common type of mutation that causes loss of Porin expression and increased resistance to cefoxitin in Klebsiella pneumoniae. This mechanism also operates in vivo: of 13 Porin-deficient cefoxitin-resistant clinical isolates of K. pneumoniae, 4 presented ISs in their ompK36 gene.
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Porin expression in clinical isolates of Klebsiella pneumoniae.
Microbiology, 1999Co-Authors: Santiago Hernández-allés, Sebastián Albertí, Luis Martínez-martínez, Antonio Doménech-sánchez, Juan M. Tomás, Dolores Álvarez, José Ignacio Burgos Gil, Vicente J. BenedíAbstract:Two Porins, OmpK36 and OmpK35, have been described previously in Klebsiella pneumoniae, and they are homologous to the Escherichia coli Porins OmpC and OmpF, respectively, at both the DNA and amino acid levels. Optimal resolution of the two K. pneumoniae Porins by electrophoresis on polyacrylamide gels is not achieved using gel systems already described for E. coli and requires modifications of the bisacrylamide content of the resolving gels. Once resolved, identification of Porins OmpK36 and OmpK35 cannot be based solely on their apparent molecular masses since in some strains the OmpK36 Porin migrates faster than the OmpK35 Porin, whilst in other strains OmpK35 is the faster-migrating Porin. Expression of OmpK35 Porin is increased in low-osmolarity medium and, combined with Western blot analysis, this allows for the identification of both Porins. Application of this identification system showed that most isolates lacking expression of extended-spectrum β-lactamases express the two Porins, whereas most isolates producing these β-lactamases express only Porin OmpK36, and the OmpK35 Porin is either very low or not expressed.
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Identification and characterization of a new Porin gene of Klebsiella pneumoniae: Its role in β-lactam antibiotic resistance
Journal of Bacteriology, 1999Co-Authors: Antonio Doménech-sánchez, Santiago Hernández-allés, Vicente J. Benedí, Luis Martínez-martínez, Sebastián AlbertíAbstract:Klebsiella pneumoniae Porin genes were analyzed to detect mutations accounting for the Porin deficiency observed in many beta-lactam-resistant strains. PCR and Southern blot analysis revealed the existence of a third Porin gene in addition to the OmpK36 and OmpK35 Porin genes previously described. This new Porin gene was designated ompK37 and is present in all of the clinical isolates tested. The OmpK37 Porin gene was cloned, sequenced, and overexpressed in Escherichia coli. In contrast to that of the major Porins, OmpK37 Porin expression was only detectable by Western blot analysis in Porin-deficient beta-lactam-resistant strains, suggesting strong down regulation under standard laboratory conditions. Functional characterization suggested a narrower pore for the OmpK37 Porin than for K. pneumoniae Porins OmpK36 and OmpK35. This correlated with the susceptibility to certain beta-lactam antibiotics, since a K. pneumoniae strain expressing Porin OmpK37, but not Porin OmpK36 or OmpK35, was less susceptible to beta-lactam antibiotics than the same strain expressing either Porin OmpK36 or OmpK35.
Susanne Reymann - One of the best experts on this subject based on the ideXlab platform.
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Purification procedure and monoclonal antibodies: two instruments for research on vertebrate Porins.
Analytical biochemistry, 1999Co-Authors: Susanne Reymann, Ziba Kiafard, Beate Rohm, Nathalie Strutz, Dörte Hesse, Hartmut Kratzin, Bodo Zimmermann, Friedrich P. Thinnes, Norbert HilschmannAbstract:On Western blots of skeletal muscle preparations of different vertebrate classes, four monoclonal anti-human type 1 Porin antibodies recognize one single band of either 30.5 or 31 kDa, respectively. To confirm that it is eukaryotic Porin which is labeled by the antibodies, we used a purification procedure developed for human type 1 Porin for Porins from skeletal muscle of shark, frog, and turkey. Applied to different mammalian species and tissues, this procedure exclusively provides type 1 Porin. However, applied to shark skeletal muscle, it provides two Porin isotypes in nearly equal amounts. In the case of frog skeletal muscle, the procedure provides mainly type 2 Porin and a lower amount of type 1 Porin. Applied to turkey skeletal muscle, the method provides exclusively type 2 Porin. As demonstrated by two-dimensional Western blots, both shark and frog Porin isotypes and the turkey type 2 Porin are recognized by our antibodies. Furthermore, we elucidated the entire amino acid sequence of frog type 2 Porin.
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NEW FINDINGS CONCERNING VERTEBRATE Porin
Die Naturwissenschaften, 1997Co-Authors: Friedrich P. Thinnes, Susanne ReymannAbstract:Eukaryotic Porin can be considered to be a good candidate for forming the channel component of the protein complex which, depending on the approach used, may realize its expression either as the outwardly-rectifying depolarization-induced chloride channel or as the volume-sensitive organic osmolyte-anion channel. As a basis for this proposition, we point to a series of correspondences in properties between mammalian Porin and the ORDIC channel complex. Specifically, mammalian Porin is expressed in the plasmalemma of different cells and chloride channels can be blocked by anti-human Porin antibodies in astrocytes and endothelial cells. There is an indication of colocalisation of human Porin and the cystic fibrosis (CF) gene product, CFTR, in the apical region of epithelial cells. The primary structure of Porin from a CF patient was found to be normal. Cytosol and amniotic fluid fractions influence the channel characteristics of mammalian Porin. Channel-active mammalian Porin binds ATP and the stilbene disulphonate grouping of the chloride channel inhibitor DIDS. Human Porin in black membranes is a pathway for taurine, and biogenic polyamines reduce the voltage dependence of human Porin. Assuming the relationship between human Porin and the ORDIC channel/VSOAC complex, studies on plasmalemma-integrated human Porin have a relevance for CF research. In addition, we refer to a case study on a child with encephalomyopathy in which Porin could not be detected using monoclonal anti-human Porin antibodies. Our studies were based on purified and sequenced human Porin from different cells and from different cell compartments. In addition, we raised antibodies against mature human Porin or synthetic parts of the molecule. This provided a firm foundation for our topochemical work with which we were able to establish the multi-topological expression of eukaryotic Porin channels. The data are summarized and discussed.
Thomas Becker - One of the best experts on this subject based on the ideXlab platform.
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Porins as helpers in mitochondrial protein translocation.
Biological chemistry, 2020Co-Authors: Alexander Grevel, Thomas BeckerAbstract:Mitochondria import the vast majority of their proteins via dedicated protein machineries. The translocase of the outer membrane (TOM complex) forms the main entry site for precursor proteins that are produced on cytosolic ribosomes. Subsequently, different protein sorting machineries transfer the incoming preproteins to the mitochondrial outer and inner membranes, the intermembrane space, and the matrix. In this review, we highlight the recently discovered role of Porin, also termed voltage-dependent anion channel (VDAC), in mitochondrial protein biogenesis. Porin forms the major channel for metabolites and ions in the outer membrane of mitochondria. Two different functions of Porin in protein translocation have been reported. First, it controls the formation of the TOM complex by modulating the integration of the central receptor Tom22 into the mature translocase. Second, Porin promotes the transport of carrier proteins toward the carrier translocase (TIM22 complex), which inserts these preproteins into the inner membrane. Therefore, Porin acts as a coupling factor to spatially coordinate outer and inner membrane transport steps. Thus, Porin links metabolite transport to protein import, which are both essential for mitochondrial function and biogenesis.
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Mitochondrial Porin links protein biogenesis to metabolism.
Current genetics, 2019Co-Authors: Kim Nguyen Doan, Lars Ellenrieder, Thomas BeckerAbstract:In this report, we summarize recent findings about a role of the outer membrane metabolite channel VDAC/Porin in protein import into mitochondria. Mitochondria fulfill key functions for cellular energy metabolism. Their biogenesis involves the import of about 1000 different proteins that are produced as precursors on cytosolic ribosomes. The translocase of the outer membrane (TOM complex) forms the entry gate for mitochondrial precursor proteins. Dedicated protein translocases sort the preproteins into the different mitochondrial subcompartments. While protein transport pathways are analyzed to some detail, only little is known about regulatory mechanisms that fine-tune protein import upon metabolic signaling. Recently, a dual role of the voltage-dependent anion channel (VDAC), also termed Porin, in mitochondrial protein biogenesis was reported. First, VDAC/Porin promotes as a coupling factor import of carrier proteins into the inner membrane. Second, VDAC/Porin regulates the formation of the TOM complex. Thus, the major metabolite channel in the outer membrane VDAC/Porin connects protein import to mitochondrial metabolism.
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dual role of mitochondrial Porin in metabolite transport across the outer membrane and protein transfer to the inner membrane
Molecular Cell, 2019Co-Authors: Lars Ellenrieder, Kim Nguyen Doan, Nikolaus Pfanner, Martin Philipp Dieterle, Christoph U Martensson, Alessia Floerchinger, Maria Luisa Campo, Thomas BeckerAbstract:The mitochondrial inner membrane harbors a large number of metabolite carriers. The precursors of carrier proteins are synthesized in the cytosol and imported into mitochondria by the translocase of the outer membrane (TOM) and the carrier translocase of the inner membrane (TIM22). Molecular chaperones in the cytosol and intermembrane space bind to the hydrophobic precursors to prevent their aggregation. We report that the major metabolite channel of the outer membrane, termed Porin or voltage-dependent anion channel (VDAC), promotes efficient import of carrier precursors. Porin interacts with carrier precursors arriving in the intermembrane space and recruits TIM22 complexes, thus ensuring an efficient transfer of the precursors to the inner membrane translocase. Porin channel mutants impaired in metabolite transport are not disturbed in carrier import into mitochondria. We conclude that Porin serves distinct functions as outer membrane channel for metabolites and as coupling factor for protein translocation into the inner membrane.
Georg E. Schulz - One of the best experts on this subject based on the ideXlab platform.
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Asymmetric conductivity of engineered Porins
Protein engineering, 2002Co-Authors: Michael Bannwarth, Georg E. SchulzAbstract:Positively charged peptide segments of 16 and 18 residues were inserted at a periplasmic turn of the Porin from Rhodobacter blasticus in order to form an electric fielddependent plug. The X-ray diffraction analysis of a mutant confirmed that the structure of the Porin had remained intact and that the insert was mobile. Incorporation experiments of single molecules into lipid bilayers showed that the distribution of electric conduction increments depended on the field polarity. The observed distributions are explained if the Porin molecules enter the bilayer preferentially with their periplasmic surface first. Furthermore, the conduction of membrane-incorporated Porin mutants changed reproducibly on field reversal showing asymmetries of ~15%, while the wild-type remained constant. This asymmetry is most likely caused by the electric field pressing the charged insert onto the pore eyelet in one field direction and removing it from the eyelet in the other. The results encourage attempts to improve the inserts in order to eventually reach diode characteristics.
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Prediction of the general structure of OmpF and PhoE from the sequence and structure of Porin from Rhodobacter capsulatus. Orientation of Porin in the membrane.
Biochimica et biophysica acta, 1991Co-Authors: Wolfram Welte, Jürgen Weckesser, Emile Schiltz, Manfred S. Weiss, Uwe Nestel, Georg E. SchulzAbstract:By comparing the hydrophilicity profiles and sequences of Porin from Rhodobacter capsulatus with those of OmpF and PhoE from Escherichia coli, a set of insertions and deletions for alignment of the sequences has been deduced. With this alignment a similar folding of OmpF and PhoE has been predicted as found by X-ray structure analysis of Porin from Rhodobacter capsulates. Furthermore, the orientation of the Porin trimer in the outer membrane was inferred from topological data on PhoE. According to this result a single channel of approx. 30 A diameter starts at the outer surface. Near the middle of the outer membrane bilayer this channel branches out into three separate channels, each running within a single Porin monomer to the periplasmic surface.
