Porins: Porins are protein molecules that were originally found in the outer membrane of GRAM-NEGATIVE BACTERIA and that form multi-meric channels for the passive DIFFUSION of WATER; IONS; or other small molecules. Porins are present in bacterial CELL WALLS, as well as in plant, fungal, mammalian and other vertebrate CELL MEMBRANES and MITOCHONDRIAL MEMBRANES.Bacterial Outer Membrane Proteins: Proteins isolated from the outer membrane of Gram-negative bacteria.Salmonella typhimurium: A serotype of Salmonella enterica that is a frequent agent of Salmonella gastroenteritis in humans. It also causes PARATYPHOID FEVER.Bacterial Proteins: Proteins found in any species of bacterium.Voltage-Dependent Anion Channels: A family of voltage-gated eukaryotic porins that form aqueous channels. They play an essential role in mitochondrial CELL MEMBRANE PERMEABILITY, are often regulated by BCL-2 PROTO-ONCOGENE PROTEINS, and have been implicated in APOPTOSIS.Mycobacterium smegmatis: A rapid-growing, nonphotochromogenic species of MYCOBACTERIUM originally isolated from human smegma and found also in soil and water. (From Dorland, 28th ed)Cell Membrane Permeability: A quality of cell membranes which permits the passage of solvents and solutes into and out of cells.Cadaverine: A foul-smelling diamine formed by bacterial decarboxylation of lysine.Delftia acidovorans: A species of gram-negative rod-shaped bacteria found ubiquitously and formerly called Comamonas acidovorans and Pseudomonas acidovorans. It is the type species of the genus DELFTIA.Ion Channels: Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS.beta-Lactams: Four-membered cyclic AMIDES, best known for the PENICILLINS based on a bicyclo-thiazolidine, as well as the CEPHALOSPORINS based on a bicyclo-thiazine, and including monocyclic MONOBACTAMS. The BETA-LACTAMASES hydrolyze the beta lactam ring, accounting for BETA-LACTAM RESISTANCE of infective bacteria.Lipid Bilayers: Layers of lipid molecules which are two molecules thick. Bilayer systems are frequently studied as models of biological membranes.Rhodobacter: A genus of gram-negative bacteria widely distributed in fresh water as well as marine and hypersaline habitats.Neisseria meningitidis: A species of gram-negative, aerobic BACTERIA. It is a commensal and pathogen only of humans, and can be carried asymptomatically in the NASOPHARYNX. When found in cerebrospinal fluid it is the causative agent of cerebrospinal meningitis (MENINGITIS, MENINGOCOCCAL). It is also found in venereal discharges and blood. There are at least 13 serogroups based on antigenic differences in the capsular polysaccharides; the ones causing most meningitis infections being A, B, C, Y, and W-135. Each serogroup can be further classified by serotype, serosubtype, and immunotype.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Escherichia coli Proteins: Proteins obtained from ESCHERICHIA COLI.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Neisseria: A genus of gram-negative, aerobic, coccoid bacteria whose organisms are part of the normal flora of the oropharynx, nasopharynx, and genitourinary tract. Some species are primary pathogens for humans.Enterobacter: Gram-negative gas-producing rods found in feces of humans and other animals, sewage, soil, water, and dairy products.Salmonella typhi: A serotype of SALMONELLA ENTERICA which is the etiologic agent of TYPHOID FEVER.Gene Expression Regulation, Bacterial: Any of the processes by which cytoplasmic or intercellular factors influence the differential control of gene action in bacteria.Anti-Bacterial Agents: Substances that reduce the growth or reproduction of BACTERIA.Borrelia burgdorferi: A specific species of bacteria, part of the BORRELIA BURGDORFERI GROUP, whose common name is Lyme disease spirochete.Borrelia burgdorferi Group: Gram-negative helical bacteria, in the genus BORRELIA, that are the etiologic agents of LYME DISEASE. The group comprises many specific species including Borrelia afzelii, Borellia garinii, and BORRELIA BURGDORFERI proper. These spirochetes are generally transmitted by several species of ixodid ticks.Lyme Disease: An infectious disease caused by a spirochete, BORRELIA BURGDORFERI, which is transmitted chiefly by Ixodes dammini (see IXODES) and pacificus ticks in the United States and Ixodes ricinis (see IXODES) in Europe. It is a disease with early and late cutaneous manifestations plus involvement of the nervous system, heart, eye, and joints in variable combinations. The disease was formerly known as Lyme arthritis and first discovered at Old Lyme, Connecticut.Borrelia Infections: Infections with bacteria of the genus BORRELIA.Arthropod Vectors: Arthropods, other than insects and arachnids, which transmit infective organisms from one host to another or from an inanimate reservoir to an animate host.Research Report: Detailed account or statement or formal record of data resulting from empirical inquiry.Escherichia coli: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.Staphylococcaceae: Family of gram-positive, facultatively anaerobic bacteria, in the order Bacillales. Genera include Gemella, Macrococcus, Salinicoccus, and STAPHYLOCOCCUS.Crystallization: The formation of crystalline substances from solutions or melts. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Crystallography, X-Ray: The study of crystal structure using X-RAY DIFFRACTION techniques. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Crystallography: The branch of science that deals with the geometric description of crystals and their internal arrangement. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Negative Staining: The technique of washing tissue specimens with a concentrated solution of a heavy metal salt and letting it dry. The specimen will be covered with a very thin layer of the metal salt, being excluded in areas where an adsorbed macromolecule is present. The macromolecules allow electrons from the beam of an electron microscope to pass much more readily than the heavy metal; thus, a reversed or negative image of the molecule is created.Oxalobacter formigenes: The sole species of the genus Oxalobacter consisting of straight or curved gram-negative rods with rounded ends. Cells are nonmotile, nonsporing, and use oxylates as the only source of CARBON and energy, with formate and CARBON DIOXIDE as end products. They are isolated from lake sediments and from the rumen or large bowel of humans and animals. (From Bergey's Manual of Determinative Bacteriology, 9th ed)Colicins: Bacteriocins elaborated by strains of Escherichia coli and related species. They are proteins or protein-lipopolysaccharide complexes lethal to other strains of the same species.Vibrio cholerae: The etiologic agent of CHOLERA.Vibrionaceae: A family of gram-negative bacteria whose members predominate in the bacterial flora of PLANKTON; FISHES; and SEAWATER. Some members are important pathogens for humans and animals.Virulence: The degree of pathogenicity within a group or species of microorganisms or viruses as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenic capacity of an organism is determined by its VIRULENCE FACTORS.Bile: An emulsifying agent produced in the LIVER and secreted into the DUODENUM. Its composition includes BILE ACIDS AND SALTS; CHOLESTEROL; and ELECTROLYTES. It aids DIGESTION of fats in the duodenum.Sucrose: A nonreducing disaccharide composed of GLUCOSE and FRUCTOSE linked via their anomeric carbons. It is obtained commercially from SUGARCANE, sugar beet (BETA VULGARIS), and other plants and used extensively as a food and a sweetener.Signal Transduction: The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.Models, Molecular: Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.Photography: Method of making images on a sensitized surface by exposure to light or other radiant energy.Image Processing, Computer-Assisted: A technique of inputting two-dimensional images into a computer and then enhancing or analyzing the imagery into a form that is more useful to the human observer.Adjuvants, Immunologic: Substances that augment, stimulate, activate, potentiate, or modulate the immune response at either the cellular or humoral level. The classical agents (Freund's adjuvant, BCG, Corynebacterium parvum, et al.) contain bacterial antigens. Some are endogenous (e.g., histamine, interferon, transfer factor, tuftsin, interleukin-1). Their mode of action is either non-specific, resulting in increased immune responsiveness to a wide variety of antigens, or antigen-specific, i.e., affecting a restricted type of immune response to a narrow group of antigens. The therapeutic efficacy of many biological response modifiers is related to their antigen-specific immunoadjuvanticity.Neisseria gonorrhoeae: A species of gram-negative, aerobic bacteria primarily found in purulent venereal discharges. It is the causative agent of GONORRHEA.B-Lymphocytes: Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation.Lymphocytes: White blood cells formed in the body's lymphoid tissue. The nucleus is round or ovoid with coarse, irregularly clumped chromatin while the cytoplasm is typically pale blue with azurophilic (if any) granules. Most lymphocytes can be classified as either T or B (with subpopulations of each), or NATURAL KILLER CELLS.Voltage-Dependent Anion Channel 2: Voltage-dependent anion channel 2 is a low abundance mammalian isoform of VDAC that interacts with the inactive form of BAK PROTEIN.Voltage-Dependent Anion Channel 1: Voltage-dependent anion channel 1 is the major pore-forming protein of the mitochondrial outer membrane. It also functions as a ferricyanide reductase in the PLASMA MEMBRANE.Mitochondrial Membrane Transport Proteins: Proteins involved in the transport of specific substances across the membranes of the MITOCHONDRIA.PubMed: A bibliographic database that includes MEDLINE as its primary subset. It is produced by the National Center for Biotechnology Information (NCBI), part of the NATIONAL LIBRARY OF MEDICINE. PubMed, which is searchable through NLM's Web site, also includes access to additional citations to selected life sciences journals not in MEDLINE, and links to other resources such as the full-text of articles at participating publishers' Web sites, NCBI's molecular biology databases, and PubMed Central.

Safety and immunogenicity of a Pseudomonas aeruginosa hybrid outer membrane protein F-I vaccine in human volunteers. (1/1946)

A hybrid protein [Met-Ala-(His)6OprF190-342-OprI21-83] consisting of the mature outer membrane protein I (OprI) and amino acids 190 to 342 of OprF of Pseudomonas aeruginosa was expressed in Escherichia coli and purified by Ni2+ chelate-affinity chromatography. After safety and pyrogenicity evaluations in animals, four groups of eight adult human volunteers were vaccinated intramuscularly three times at 4-week intervals and revaccinated 6 months later with either 500, 100, 50, or 20 microg of OprF-OprI adsorbed onto A1(OH)3. All vaccinations were well tolerated. After the first vaccination, a significant rise of antibody titers against P. aeruginosa OprF and OprI was measured in volunteers receiving the 100- or the 500-microg dose. After the second vaccination, significant antibody titers were measured for all groups. Elevated antibody titers against OprF and OprI could still be measured 6 months after the third vaccination. The capacity of the elicited antibodies to promote complement binding and opsonization could be demonstrated by a C1q-binding assay and by the in vitro opsonophagocytic uptake of P. aeruginosa bacteria. These data support the continued development of an OprF-OprI vaccine for use in humans.  (+info)

Distinct sensitivities of OmpF and PhoE porins to charged modulators. (2/1946)

The inhibition of the anion-selective PhoE porin by ATP and of the cation-selective OmpF porin by polyamines has been previously documented. In the present study, we have extended the comparison of the inhibitor-porin pairs by investigating the effect of anions (ATP and aspartate) and positively charged polyamines (spermine and cadaverine) on both OmpF and PhoE with the patch-clamp technique, and by comparing directly the gating kinetics of the channels modulated by their respective substrates. The novel findings reported here are (1) that the activity of PhoE is completely unaffected by polyamines, and (2) that the kinetic changes induced by ATP on PhoE or polyamines on OmpF suggest different mechanisms of inhibition. ATP induces a high degree of flickering in the PhoE-mediated current and appears to behave as a blocker of ion flow during its presumed transport through PhoE. Polyamines modulate the kinetics of openings and closings of OmpF, in addition to promoting a blocker-like flickering activity. The strong correlation between sensitivity to inhibitors and ion selectivity suggests that some common molecular determinants are involved in these two properties and is in agreement with the hypothesis that polyamines bind inside the pore of cationic porins.  (+info)

Enhanced bioaccumulation of heavy metal ions by bacterial cells due to surface display of short metal binding peptides. (3/1946)

Metal binding peptides of sequences Gly-His-His-Pro-His-Gly (named HP) and Gly-Cys-Gly-Cys-Pro-Cys-Gly-Cys-Gly (named CP) were genetically engineered into LamB protein and expressed in Escherichia coli. The Cd2+-to-HP and Cd2+-to-CP stoichiometries of peptides were 1:1 and 3:1, respectively. Hybrid LamB proteins were found to be properly folded in the outer membrane of E. coli. Isolated cell envelopes of E. coli bearing newly added metal binding peptides showed an up to 1.8-fold increase in Cd2+ binding capacity. The bioaccumulation of Cd2+, Cu2+, and Zn2+ by E. coli was evaluated. Surface display of CP multiplied the ability of E. coli to bind Cd2+ from growth medium fourfold. Display of HP peptide did not contribute to an increase in the accumulation of Cu2+ and Zn2+. However, Cu2+ ceased contribution of HP for Cd2+ accumulation, probably due to the strong binding of Cu2+ to HP. Thus, considering the cooperation of cell structures with inserted peptides, the relative affinities of metal binding peptide and, for example, the cell wall to metal ion should be taken into account in the rational design of peptide sequences possessing specificity for a particular metal.  (+info)

In-vitro selection of porin-deficient mutants of two strains of Klebsiella pneumoniae with reduced susceptibilities to meropenem, but not to imipenem. (4/1946)

We have evaluated the ability of imipenem and meropenem to select, in vitro, resistant mutants of two clinical isolates of Klebsiella pneumoniae producing both SHV and TEM beta-lactamases. Only meropenem selected mutants of both isolates for which the MICs of meropenem, but not imipenem, were markedly higher than those for the parent strains; the MICs of several other beta-lactam antibiotics, including beta-lactam/beta-lactamase inhibitor combinations, for these mutants were also higher than those for the parent strains. In contrast, the MICs for the imipenem-selected mutants were the same as, or similar to, those for the parent strains. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis revealed that an outer membrane protein in both parent strains was absent in the meropenem-selected mutants, but not in the imipenem-selected mutants. This protein is likely to be a porin, the absence of which is presumably associated with impaired beta-lactam permeability and, therefore, the reduced susceptibilities to these antibiotics exhibited by the mutant strains. We believe that this is the first report of the in-vitro selection of porin-deficient mutants of K. pneumoniae following exposure to meropenem.  (+info)

Single channel analysis of recombinant major outer membrane protein porins from Chlamydia psittaci and Chlamydia pneumoniae. (5/1946)

We recently demonstrated that the major outer membrane protein of Chlamydia psittaci, the primary vaccine candidate for combating chlamydial infections, functions as a porin-like ion channel. In this study, we have cloned, expressed and functionally reconstituted recombinant major outer membrane proteins from C. psittaci and Chlamydia pneumoniae and analysed them at the single channel level. Both form porin-like ion channels that are functionally similar to those formed by native C. psittaci major outer membrane protein. Also, like the native channels, recombinant C. psittaci channels are modified by a native major outer membrane protein-specific monoclonal antibody. This is the first time that native function has been demonstrated for recombinant chlamydial major outer membrane proteins. Future bilayer reconstitution will provide a strategy for detailed structure/function studies of this new subclass of bacterial porins and the work also has important implications for successful protein refolding and the development of improved subunit vaccines.  (+info)

Site-directed mutagenesis of loop L3 of sucrose porin ScrY leads to changes in substrate selectivity. (6/1946)

The difference in substrate selectivity of the maltodextrin (LamB) and sucrose (ScrY) porins is attributed mainly to differences in loop L3, which is supposed to constrict the lumen of the pores. We show that even a single mutation (D201Y) in loop L3 leads to a narrowing of the substrate range of ScrY to that resembling LamB. In addition, we removed the putative N-terminal coiled-coil structure of ScrY and studied the effect of this deletion on sucrose transport.  (+info)

Escherichia coli outer membrane protein TolC is involved in production of the peptide antibiotic microcin J25. (7/1946)

A Tn5 insertion in tolC eliminated microcin J25 production. The mutation had little effect on the expression of the microcin structural gene and presumably acted by blocking microcin secretion. The tolC mutants carrying multiple copies of the microcin genes were less immune to the microcin. TolC is thus likely a component of a microcin export complex containing the McjD immunity protein, an ABC exporter.  (+info)

Bcl-xL prevents cell death following growth factor withdrawal by facilitating mitochondrial ATP/ADP exchange. (8/1946)

Growth factor withdrawal is associated with a metabolic arrest that can result in apoptosis. Cell death is preceded by loss of outer mitochondrial membrane integrity and cytochrome c release. These mitochondrial events appear to follow a relative increase in mitochondrial membrane potential. This change in membrane potential results from the failure of the adenine nucleotide translocator (ANT)/voltage-dependent anion channel (VDAC) complex to maintain ATP/ADP exchange. Bcl-xL expression allows growth factor-deprived cells to maintain sufficient mitochondrial ATP/ADP exchange to sustain coupled respiration. These data demonstrate that mitochondrial adenylate transport is under active regulation. Efficient exchange of ADP for ATP is promoted by Bcl-xL expression permitting oxidative phosphorylation to be regulated by cellular ATP/ADP levels and allowing mitochondria to adapt to changes in metabolic demand.  (+info)

  • However, ToxR, independently of TcpP and ToxT, activates and represses transcription of the genes encoding two outer-membrane porins, OmpU and OmpT. (pnas.org)
  • Although genes encoding TcpP, ToxT, CT, and TCP are specifically associated with V. cholerae , ToxR is found in other Vibrio and Photobacterium species and regulates porin expression in these other bacteria as well ( 13 , 14 ). (pnas.org)
  • The sizes of PCR-amplified products from ompF -type genes are different from those of other porin genes (data not shown). (asm.org)
  • Expression levels of efflux and porin genes were mesured by real-time reverse transcription PCR. (jidc.org)
  • However, the regulation of porin genes and its own gene by CRP remains unclear in Y. pestis . (biomedcentral.com)
  • It is likely that Y. pestis OmpR and CRP respectively sense different signals (medium osmolarity, and cellular cAMP levels) to regulate porin genes independently. (biomedcentral.com)
  • Data presented here indicate a remarkable remodeling of the CRP-mediated regulation of porin genes and of its own one between these two bacteria. (biomedcentral.com)
  • Decreased susceptibility to fluoroquinolones could be partly explained by decreased expression of the outer membrane porin genes ompA and ompF with a concomitant increase in the expression of the ciprofloxacin resistance efflux pump gene acrB in Δcrp cells. (readbyqxmd.com)
  • 4 mg l -1 ), 60.5 % (115/190) showed mutation in both porin genes. (cdc.gov)
  • Occurrence of porin genes in M. fortuitum . (biomedcentral.com)
  • Intragenic recombination between porin genes of the same allelic family is likely occurring in nature because mosaic gene structure has been reported in porB genes. (cdc.gov)
  • The two classical porins OmpC and OmpF consist of three 16-stranded β barrels, each of which forms a channel that is restricted in the middle due to the inward folding of a loop ( 8 ). (asm.org)
  • Much of our knowledge of the regulatory activities of EnvZ/OmpR has been derived from studies on the regulation of the outer membrane (OM) OmpC and OmpF porins in response to changes in the osmolarity of the environment ( Russo and Silhavy, 1991 ). (frontiersin.org)
  • OmpC and OmpF are general porins that facilitate the passive and non-specific diffusion of low molecular weight hydrophilic substances across the OM ( Nikaido, 2003 ). (frontiersin.org)
  • A generally accepted view of the porin assembly pathway is that after the removal of the signal peptide from precursors, mature porin molecules transiently exist in the periplasm as soluble or peripherally membrane-associated, thermolabile intermediates. (asm.org)
  • OmpF porin is a non-specific transport channel that allows for the passive diffusion of small, polar molecules (600-700 Da in size) through the cell's outer membrane. (davidson.edu)
  • Neisserial porins induce B lymphocytes to express costimulatory B7-2 molecules and to proliferate. (rupress.org)
  • However, the OmpF porin channel allowed influx of more solute molecules per unit time than did the equivalent weight of the OmpC porin when the flux was driven by a concentration gradient of the same size. (asm.org)
  • Paper I: In Silico Structure and Sequence Analysis of Bacterial Porins and Specific Diffusion Channels for Hydrophilic Molecules: Conservation, Multimericity and Multifunctionality. (uio.no)
  • The two major porins of Escherichia coli , namely OmpF and OmpC, form non-specific transport channels and allow for the passive diffusion of small, polar molecules (such as water, ions, amino acids, and other nutrients, as well as waste products) across the cell membrane. (biomedcentral.com)
  • The over-expression of OmpX can balance the decreased expression of non-specific porins, OmpF and OmpC, for the exclusion of small harmful molecules. (biomedcentral.com)
  • Moreover, S. Typhi porins induce the expression of costimulatory molecules on antigen-presenting cells through toll-like receptor canonical signaling pathways. (readbyqxmd.com)
  • Among a panel of independent V. cholerae rpoE mutants, more than 75% contain suppressor mutations that reduce production of OmpU, V. cholerae's principal outer membrane porin. (harvard.edu)
  • ATR-FTIR spectroscopy proved to reliably distinguish between several E. coli porin mutants with an accuracy not replicated by FTIR in transmission mode (using previously optimized procedures). (spectroscopynow.com)
  • In addition, mutants of OmpF and NanC have been generated to modify ion conductance properties of these porins. (jacobs-university.de)
  • Although we confirm the findings of Fiedler and Rotering, we find that the regulation of OmpF and OmpC expression in mdoA mutants is normal in cells grown on other low- osmolarity media, eliminating the possibility that MDO itself might control porin expression. (princeton.edu)
  • Characterization of -Lactamase and Porin Mutants of Enterobacteriaceae Selected with Ceftaroline + Avibactam (NXL104). (uea.ac.uk)
  • The outer membrane porins such as OmpK35 and OmpK36 were analysed by SDS-PAGE, PCR, and sequencing methods. (hindawi.com)
  • Outer membrane porin, OmpK35, was detected in 30 (62.5%) of 48 ESBL-producing isolates while OmpK36 was found in 35 (72.91%) of 48 ESBL-producing isolates. (hindawi.com)
  • Carbapenem resistance in K. pneumoniae is based on various mechanisms that may involve carbapenemase production, upregulation of efflux pumps, or loss of porins, including OmpK35, OmpK36, and OmpK37. (hindawi.com)
  • OmpK35 from Klebsiella pneumoniae is the homologue of Escherichia coli OmpF porin. (asm.org)
  • Klebsiella pneumoniae produces two major porins (OmpK35 and OmpK36) and the quiescent porin OmpK37. (asm.org)
  • Most clinical isolates of K. pneumoniae lacking extended-spectrum β-lactamase (ESBL) express both OmpK35 and OmpK36 porins, while most ESBL-expressing K. pneumoniae clinical isolates produce only OmpK36 ( 9 ). (asm.org)
  • Preliminary results ( 6 ) indicate that OmpK35 allows efficient penetration of cefoxitin, cefotaxime, and carbapenems, but there has been some controversy on the role of this porin in cephalosporin penetration in K. pneumoniae ( 18 ). (asm.org)
  • Recombinants were screened for ompK35 by PCR using primers U681 (5′-CGG TTA CGG CCA GTG GGA ATA-3′) and L1316 (5′-GAC GCA GAC CGA AAT CGA ACT-3′), specific for enterobacterial porins and located 215 and 850 bp downstream of the ompK36 start codon, respectively ( 6 ). (asm.org)
  • The expression of OmpK35 was downregulated in a high-osmolarity culture medium, as occurs with the OmpF-like porins ( 9 ), and OmpK35 reacted with anti-OmpK35 in immunoblot experiments (data not shown). (asm.org)
  • The OmpK35 protein expressed by the E. coli clone was extracted by porin extraction methods based on the trypsin resistance of porins and their strong noncovalent association with the peptidoglycan, and it also retained its heat modifiability. (asm.org)
  • To understand the diversity of porin disruption in Klebsiella pneumoniae, the major outer membrane protein (OMP) porins, OmpK35 and OmpK36, were examined in a set of isolates that did not harbour traditional carbapenem-hydrolysing enzymes, but nevertheless tested non-susceptible to ertapenem. (cdc.gov)
  • The statistical data were combined with experimental knowledge about porin insertion to prepare the model of porin insertion into the outer membrane. (srce.hr)
  • Omp32, the strongly anion-selective porin from Comamonas acidovorans, has been crystallized. (uni-konstanz.de)
  • We have recently reported simple and versatile artificial membrane pore analogues-carbon nanotube porins (CNTPs)-short segments of single-wall carbon nanotubes that can self-insert into the lipid membrane and form a transmembrane pore [ 10 ]. (royalsocietypublishing.org)
  • ipeX was localized within an untranslated region of 247 base pairs between the stop codon of nmpC -a remnant porin gene from the cryptic phage qsr ′ (DLP12) genome-and its predicted Rho-independent transcriptional terminator. (asm.org)
  • The OmpF porin gene contains 1807 nucleotide bases. (davidson.edu)
  • Isolates without obvious genetic lesions in either major porin gene were further examined by outer membrane protein SDS-PAGE. (cdc.gov)
  • The promoter region of the oprB gene was cloned into a lacZ transcriptional fusion vector, and the construct was mobilized into P. aeruginosa OprB-deficient strain, WW100, to evaluate additional environmental factors that influence OprB porin gene expression. (umanitoba.ca)
  • In addition, our data showed that OmpR is responsible for up regulation of the kdgM1 gene encoding the second specific oligogalacturonide porin KdgM1. (frontiersin.org)
  • Earlier we have reported the extreme thermal stability of porin from Paracoccus denitrificans reconstituted into liposomes. (uni-konstanz.de)
  • Our results show that a mixed lipid system (non-uniform bilayer) optimizes the thermal stability of porin as compared to the porin in pure lipids (uniform bilayer) or detergent micelles. (uni-konstanz.de)
  • Our results indicate that ToxR-dependent modulation of the outer membrane porins OmpU and OmpT is critical for V. cholerae bile resistance, virulence factor expression, and intestinal colonization. (pnas.org)
  • ToxR, however, independently of the transcriptional activators TcpP and ToxT, modulates expression of two outer membrane porins, OmpU and OmpT ( 8 - 10 ). (pnas.org)
  • Thus, ToxR-dependent modulation of porins apparently preceded, and possibly contributed to, the evolution of V. cholerae as a human pathogen, but little is known about the potential role of OmpU and OmpT in V. cholerae pathogenesis. (pnas.org)
  • V. cholerae strains were genetically manipulated to force a "porin swap," i.e., a toxR + strain that expresses OmpT in place of OmpU and a toxR − strain that expresses OmpU in place of OmpT. (pnas.org)
  • A matrix-destined precursor and the porin precursor compete for the same translocation sites in both normal mitochondria and mitochondria whose surface receptors have been removed, suggesting that both precursors utilize the general import pore. (nih.gov)
  • The Escherichia coli porin OmpG, which acts as an efficient unspecific channel for mono-, di- and trisaccharides, has been purified and crystallized in two dimensions. (nih.gov)
  • Membrane-derived oligosaccharides (MDO's) promote closing of an E. coli porin channel. (nih.gov)
  • Finally, the biological relevance of two porins, P13 and P66, was demonstrated in a double mutant displaying a stress response as revealed by increased sensitivity to high osmolarity and elevated expression of the B. burgdorferi heat-shock protein HtrA homolog. (diva-portal.org)
  • This mutant porin and its derivative, OmpC R74C,G154C , or OmpC 2Cys ( 17 ), are the subjects of this work and are further discussed below. (asm.org)
  • Considering the colicin resistance of the mutant, it is inferred that in vivo, colicin N traverses the outer membrane through the porin channel or that the dynamics of the exposed loops are affected in the mutant such that these may impede the binding of the toxin. (pnas.org)
  • Hoenger A, Ghosh R, Schoenenberger CA, Aebi U, Engel A. Direct in situ structural analysis of recombinant outer membrane porins expressed in an OmpA-deficient mutant Escherichia coli strain. (ucdenver.edu)
  • When the mitochondria were preincubated at 37°C, the assembly of porin in the tom40 mutant mitochondria was similarly reduced compared with wild-type mitochondria. (nih.gov)
  • The assembly of porin was inhibited in the mutant mitochondria (Fig. 8 A, lanes 4-9). (nih.gov)
  • This interaction was independent of the immobilized binding partner (porin reconstituted in liposomes or MtCK) or the analyzed isoform (chicken sarcomeric MtCK or human ubiquitous MtCK, human recombinant porin, or purified bovine porin). (inserm.fr)
  • Top: Schematic showing CNT porin preparation and incorporation into liposomes. (lbl.gov)
  • Here, the lysogenization event leads to the expression of a phage-encoded porin, Lc, and the inhibition of the host's OmpC porin. (asm.org)
  • The work conducted in this study will shed light on how phage porin expression regulates that of ompC . (asm.org)
  • Neisserial porins increased the surface expression of the costimulatory ligand B7-2 (CD86) but did not affect the expression of B7-1 (CD80). (rupress.org)
  • Herein, both transmission Fourier-transform infrared (FTIR) and attenuated total reflectance (ATR)-FTIR spectroscopy are used to analyse E. coli strains that differ solely in their porin expression profile. (spectroscopynow.com)
  • Growth temperature, pH of the growth medium, salicylate concentration, and carbohydrate source were found to differentially influence porin expression. (umanitoba.ca)
  • Moreover, the porin precursor can be cross-linked to Tom20, Tom22, and Tom40 on its import pathway. (nih.gov)
  • A) Radiolabeled porin precursor (10 μl reticulocyte lysate per lane) was incubated with isolated yeast mitochondria as indicated (50 μg protein per lane) at 25°C. The mitochondria were reisolated, lysed in digitonin-containing buffer, and subjected to BN-PAGE and digital autoradiography. (nih.gov)
  • Understand how antibiotics diffuse through these porins can help researcher to develop new antibiotics with an improved penetration especially when resistance becomes a serious problem for infectious disease. (unica.it)
  • The results of this study favour the use of porins as a common immunogen to control salmonellosis since porin patterns were found to be quite similar among the serotypes of salmonellae, unlike other enterobacterial species. (ac.ir)