The neisserial porins are the major protein components of the outer membrane of the pathogenic Neisseria (N. meningitidis and N. gonorrhoeae). They have been shown to be able to enhance the immune response to poorly immunogenic substances (e.g., polysaccharides, peptides, glycolipids, etc.). To explore the basis of their potent adjuvant activity, the effect of the neisserial porins on T-B cell interactions and T cell costimulation was examined. Neisserial porins increased the surface expression of the costimulatory ligand B7-2 (CD86) but did not affect the expression of B7-1 (CD80). In addition, incubation with the neisserial porins increased the T lymphocyte costimulatory ability of B lymphocytes, which was inhibited by anti-B7-2 but not anti-B7-1 monoclonal antibodies. Upregulation of B7-2 on the surface of B lymphocytes may be the mechanism behind the immunopotentiating activity of neisserial porins. ...
The membrane assembly of outer membrane proteins is more complex than that of transmembrane helical proteins owing to the intervention of many charged and polar residues in the membrane. Accordingly, the predictive accuracy of transmembrane beta strands is considerably lower than that of transmembrane alpha helices. In this paper we develop a set of conformational parameters for membrane spanning beta strands. We formulate an algorithm to predict the transmembrane beta strands in the family of bacterial porins based on the conformational parameters and surrounding hydrophobicities of amino acid residues. A Fortran program has been developed which takes the amino acid sequence as the input file and gives the predicted transmembrane beta strand as output. The present method predicts at an accuracy level of 82% for all the bacterial porins considered.
The Tar chemoreceptor of Escherichia coli is a membrane-bound sensory protein that facilitates bacterial chemotaxis in response to aspartate. The EnvZ molecule has a membrane topology similar to Tar and is a putative osmosensor that is required for osmoregulation of the genes for the major outer membrane porin proteins, OmpF and OmpC. The cytoplasmic signaling domain of Tar was replaced with the carboxyl portion of EnvZ, and the resulting chimeric receptor activated transcription of the ompC gene in response to aspartate. The activation of ompC by the chimeric receptor was absolutely dependent on OmpR, a transcriptional activator for ompF and ompC. ...
Structural relatedness of enteric bacterial porins assessed with monoclonal antibodies to Salmonella typhimurium OmpD and OmpC.: The immunochemistry and structu
Outer membrane porin D is a protein family containing bacterial outer membrane porins which are involved in transport of cationic amino acids, peptides, antibiotics and other compounds. It was also described as having some serine protease activity. However many of these proteins are not peptidases and are classified as non-peptidase homologues as they either have been found experimentally to be without peptidase activity, or lack amino acid residues that are believed to be essential for the catalytic activity of peptidases in the S43 family. Yoshihara E, Yoneyama H, Ono T, Nakae T (June 1998). "Identification of the catalytic triad of the protein D2 protease in Pseudomonas aeruginosa". Biochem. Biophys. Res. Commun. 247 (1): 142-5. doi:10.1006/bbrc.1998.8745. PMID 9636669. This article incorporates text from the public domain Pfam and InterPro ...
The proper functioning of proteins requires their correct localization to predetermined cellular locations. In the gram-negative bacterium Escherichia coliK-12, a special class of proteins known as porins (24) must be properly targeted and assembled in the outer membrane to form channels that facilitate the diffusion of hydrophilic solutes. The atomic structure showed that porins primarily consist of antiparallel β strands that are arranged in a pseudocyclic β-barrel structure, which encloses a water-filled channel (6, 29). On the periplasmic side, β strands are adjoined by short turns, whereas long loops provide connections on the medium-exposed side. Although the majority of loops are surface exposed, one or more loops fold inward thus restricting the channel. Surface-exposed loops are often utilized by bacteriophages as their receptors (35, 36, 37).. Outer membrane proteins (OMPs) are synthesized in the cytoplasm as precursors with an amino-terminal signal sequence that assists in exiting ...
Gram-negative bacteria are protected against external attack by an outer membrane. However, general diffusion porins located in this membrane allow the entry, by simple diffusion, of small molecules and, among them, antibiotics (beta-lactams and fluoroquinolones). Strains of bacteria resistant to beta-lactams have shown either a low porin density in the outer membrane, or some mutations at the level of porins affecting their internal size. 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. Recent experimental investigations pointed out how the diffusion of antibiotics through a porin is a molecular-based process: during diffusion the antibiotics interact strongly with the amino acids of the porin. Changing either the charge or the hydrophobicity of antibiotics the interaction strenght with the porin changes as well. Using a recent algorithm ...
A strain of Escherichia coli, selected on the basis of its resistance to colicin N, reveals distinct structural and functional alterations in unspecific OmpF porin. A single mutation [Gly-119--,Asp (G119D)] was identified in the internal loop L3 that contributes critically to the formation of the construction inside the lumen of the pore. X-ray structure analysis to a resolution of 3.0 A reveals a locally altered peptide backbone, with the side chain of residue Asp-119 protruding into the channel, causing the area of the constriction (7 x 11 A in the wild type) to be subdivided into two intercommunicating subcompartments of 3-4 A in diameter. The functional consequences of this structural modification consist of a reduction of the channel conductance by about one-third, of altered ion selectivity and voltage gating, and of a decrease of permeation rates of various sugars by factors of 2-12. The structural modification of the mutant protein affects neither the beta-barrel structure nor those ...
Sucrose-specific porin, molecular model. Porins are proteins that span cell membranes and act as a channel through which specific molecules can diffuse. - Stock Image F009/5873
1GFM: Structural and functional characterization of OmpF porin mutants selected for larger pore size. I. Crystallographic analysis.
figure taken from the reference below). Murein means peptidoglycan cell wall and the cytoplasm denotes the inside of the cell. In this scenario, the double-membraned proto-bacteria (which has spend the last half-a-billion years or so evolving a well adjusted double membrane system) suddenly looses the outer membrane. A very simple genetic change would lead to a massively overgrown cell wall, which would rip the outer membrane away. The cell looses all its outer membrane porins, and signal systems, but in return gains a highly protective cell wall, which potentially allows it to survive in different niches. How these aspects are lost genetically is another matter, and the paper rather hand-waves away by saying that unused genes tend to get lost eventually. Which is true in bacteria, they have such a small genome they dont want it getting filled up with unnecessary genes, but I have a feeling genes tend to leave something behind. Even so, the question of where the now-unnecessary genes go is ...
1GFN: Structural and functional characterization of OmpF porin mutants selected for larger pore size. I. Crystallographic analysis.
Phylogenetic analysis was utilized to investigate biological relationships (tissue tropism, disease presentation, and epidemiologic success), as evidenced by coevolution, among human strains ofChlamydia trachomatis. Nucleotide sequences ofomp1, the gene encoding the major outer membrane protein (MOMP) of C. trachomatis, were determined for 40 strains representing 11 serovars. These data were combined with availableomp1 sequences from GenBank for an analysis encompassing a total of 69 strains representing 17 serovars infecting humans. Phylogenetic analysis of the nucleotide and inferred amino acid sequences showed no evolutionary relationships among serovars that corresponded to biological or pathological phenotypes (tissue tropism, disease presentation, and epidemiologic success). In addition, no specific residues that may have evolved to play a role in determining biologically relevant characteristics of chlamydia, such as tissue specificity, disease presentation, and epidemiologic success, ...
A vaccine against C. trachomatis infection has proven difficult to develop. Early vaccine studies showed that whole inactivated bacterial cells administered intramuscularly were partially protective in human and primate trials. Primate vaccine trials and human experimental infection studies suggested that C. trachomatis immunity was in part strain specific, and the identification of MOMP as the strain-specific antigen of C. trachomatis quickly focused vaccine efforts on this protein. In general, use of MOMP or peptide epitopes derived from it as a vaccine has engendered variable or no protective immunity in a variety of animal model systems. The best results were observed when MOMP was used as a structurally intact molecule, suggesting that conformationally intact antigenic sites on the molecule are important for protective immunity.. We previously reported that MOMP DNA administered parenterally was also partially effective in inducing protective immunity against lung infection with MoPn. The ...
In the current study, the construction of a toxR+ V. cholerae strain that expresses the ToxR-repressed porin OmpT in place of the ToxR-activated porin OmpU has allowed us to dissect the role these porins play in V. cholerae pathogenesis. Amazingly, merely substituting one outer membrane porin for another resulted in a number of attenuated pathogenic properties, including bile resistance, virulence factor expression, and intestinal colonization. ToxR-dependent regulation of outer membrane porins appears to have preceded the evolution of V. cholerae, because ToxR performs similar functions in other members of the Vibrionaceae (14, 17). However, these other bacteria do not have the additional regulatory factors TcpP and ToxT whose genes are located on the V. cholerae-specific pathogenicity island VPI (30). The recruitment of the ancestral ToxR protein into the virulence regulatory cascade involving recently acquired elements ties porin regulation to pathogenesis. We suggest that the contribution of ...
Ertapenem is a potent carbapenem antibiotic for most clinical isolates of Klebsiella pneumoniae, with a typical MIC at which 90% of the isolates tested are inhibited of 0.03 to 0.06 μg/ml (6, 9), but occasional strains for which the MICs are ≥16 μg/ml have been detected (6, 7). In one such strain resistance was dependent on the presence of the plasmid-mediated extended-spectrum β-lactamase (ESBL) SHV-2 and additional host events presumably affecting ertapenem permeativity (7). Further studies were undertaken to elucidate the contribution of β-lactamase and host mutation to such exceptional resistance.. The K. pneumoniae strain for which the ertapenem MIC was 16 μg/ml was treated with ethidium bromide to cure the resident plasmid. The ertapenem MIC for the resulting strain, C2, was still elevated at l μg/ml, and the strain was found to be defective in expression of outer membrane porins OmpK35 and OmpK36 (10). To evaluate the influence of different β-lactamases on the ertapenem ...
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As we compare the condition of the world to-day with its condition at any former period, we find a marked differ- ence in the sentiments of the masses. The spirit of inde- pendence is now abroad, and men are not so easily blind- folded, deceived and led by rulers and politicians, and therefore they will not submit to the yokes of former days. This change of public sentiment has not been a gradual one from the very beginning of mans effort to govern L t pi- self, but clearly marked only as far back as the sixteenth century ; and its progress has been most rapid within the last fifty years. This change, therefore, is not the result of the experience of past ages, but is the natural result of the recent increase and general diffusion of knowledge among the masses of mankind. The preparation for this general diffusion of knowledge began with the invention of printing, about 1440 A. D., and the consequent multiplica- tion of books and news periodicals. The influence of this invention in the general ...
The asymmetric outer membrane of Gram-negative bacteria is formed of the inner leaflet with phospholipids and the outer leaflet with lipopolysaccharides (LPS). Outer membrane protein F (OmpF) is a trimeric porin responsible for the passive transport of small molecules across the outer membrane of Escherichia coli. Here, we report the impact of different levels of heterogeneity in LPS environments on the structure and dynamics of OmpF using all-atom molecular dynamics simulations. The simulations provide insight into the flexibility and dynamics of LPS components that are highly dependent on local environments, with lipid A being the most rigid and O-antigen being the most flexible. Increased flexibility of O-antigen polysaccharides is observed in heterogeneous LPS systems, where the adjacent O-antigen repeating units are weakly interacting and thus more dynamic, compared to homogeneous LPS systems in which LPS interacts strongly with each other with limited overall flexibility due to dense ...
Pseudomonas aeruginosa is an important opportunistic pathogen that can cause chronic and often life-threatening infections of the respiratory tract, particularly in individuals with cystic fibrosis (CF). Because infections with P. aeruginosa remain the major cause of the high morbidity and mortality of CF, a vaccine against P. aeruginosa would be very useful for preventing this disorder. The outer membrane protein F (OprF) of P. aeruginosa is a promising vaccine candidate and various B cell epitopes within OprF have been identified. Given that adenovirus (Ad) vectors have strong immunogenic potential and can function as adjuvants for genetic vaccines, the present study evaluates the immunogenic and protective properties of a novel replication-deficient Ad vector in which the Ad hexon protein was modified to include a 14-amino acid epitope of P. aeruginosa OprF (Epi8) in loop 1 of the hypervariable region 5 of the hexon (AdZ.Epi8). Immunization of C57BL/6 mice with AdZ.Epi8 resulted in detectable ...
Dispensable loops shield the functionally-important extracellular loops of the essential Gram-negative bacterial outer membrane protein LptD from antibody interference.
Anand A, LeDoyt M, Karanian C, Luthra A, Koszelak-Rosenblum M, Malkowski MG, Puthenveetil R, Vinogradova O, Radolf JD. Bipartite Topology of Treponema pallidum Repeat Proteins C/D and I: OUTER MEMBRANE INSERTION, TRIMERIZATION, AND PORIN FUNCTION REQUIRE A C-TERMINAL ß-BARREL DOMAIN. J Biol Chem. 2015 May 08; 290(19):12313-31 ...
In biochemistry, a protein trimer is a macromolecular complex formed by three, usually non-covalently bound, macromolecules like proteins or nucleic acids. A homo-trimer would be formed by three identical molecules. A hetero-trimer would be formed by three different macromolecules. Type II Collagen is an example of homo-trimeric protein. Porins usually arrange themselves in membranes as trimers. ...
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A - Tilt: 3° - Segments: 1( 6- 16), 2( 31- 39), 3( 43- 50), 4( 68- 78), 5( 85- 92), 6( 111- 120), 7( 128- 136), 8( 151- 160), 9( 167- 174), 10( 192- 201), 11( 204- 214), 12( 223- 230), 13( 237- 244), 14( 259- 268 ...
A - Tilt: 5° - Segments: 1( 6- 16), 2( 31- 41), 3( 42- 50), 4( 68- 78), 5( 84- 92), 6( 111- 122), 7( 127- 135), 8( 151- 161), 9( 166- 173), 10( 192- 200), 11( 204- 212), 12( 234- 244), 13( 247- 256), 14( 271- 279 ...
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Phlogenzym je obvykle dobre znášaný, ani pri dlhodobom užívaní vysokých dávok neboli pozorované nežiaduce účinky. Pôsobením enzýmov môžu nastať neškodné zmeny farby, pachu a konzistencie stolice. Počas užívania vyšších jednorázových dávok sa môžu objaviť pocity plnosti, nafukovania a výnimočne pocit nevoľnosti. Tomu sa dá zabrániť rozdelením dávky na viacero dávok v priebehu dňa. Ak tieto príznaky aj po znížení dávky pretrvávajú, poraďte sa s lekárom. Zriedka pozorované alergické reakcie (kožná vyrážka) odoznejú po vysadení lieku. Pri ich prípadnom výskyte prerušte užívanie Phlogenzymu a poraďte sa s lekárom. Zriedkavými nežiaducimi účinkami sú: bolesť hlavy, pocit hladu a zvýšená potivosť. S lekárom sa o ďalšom užívaní Phlogenzymu poraďte aj v prípade výskytu akýchkoľvek neobvyklých reakcií ...
The Dashs sock-like bootie design, which keeps out debris, is combined with arch-lasted construction for a supportive fit. Lacing is asymmetrical with offset eyelets that help to reinforce the support.
p>The checksum is a form of redundancy check that is calculated from the sequence. It is useful for tracking sequence updates.,/p> ,p>It should be noted that while, in theory, two different sequences could have the same checksum value, the likelihood that this would happen is extremely low.,/p> ,p>However UniProtKB may contain entries with identical sequences in case of multiple genes (paralogs).,/p> ,p>The checksum is computed as the sequence 64-bit Cyclic Redundancy Check value (CRC64) using the generator polynomial: x,sup>64,/sup> + x,sup>4,/sup> + x,sup>3,/sup> + x + 1. The algorithm is described in the ISO 3309 standard. ,/p> ,p class="publication">Press W.H., Flannery B.P., Teukolsky S.A. and Vetterling W.T.,br /> ,strong>Cyclic redundancy and other checksums,/strong>,br /> ,a href="http://www.nrbook.com/b/bookcpdf.php">Numerical recipes in C 2nd ed., pp896-902, Cambridge University Press (1993),/a>),/p> Checksum:i ...
The protein encoded by this gene belongs to the BCL2 protein family. BCL2 family members form hetero- or homodimers and act as anti- or pro-apoptotic regulators that are involved in a wide variety of cellular activities. This protein forms a heterodimer with BCL2, and functions as an apoptotic activator. This protein is reported to interact with, and increase the opening of, the mitochondrial voltage-dependent anion channel (VDAC), which leads to the loss in membrane potential and the release of cytochrome c. The expression of this gene is regulated by the tumor suppressor P53 and has been shown to be involved in P53-mediated apoptosis. Multiple alternatively spliced transcript variants, which encode different isoforms, have been reported for this gene. Product Name ...
The protein encoded by this gene belongs to the BCL2 protein family. BCL2 family members form hetero- or homodimers and act as anti- or pro-apoptotic regulators that are involved in a wide variety of cellular activities. This protein forms a heterodimer with BCL2, and functions as an apoptotic activator. This protein is reported to interact with, and increase the opening of, the mitochondrial voltage-dependent anion channel (VDAC), which leads to the loss in membrane potential and the release of cytochrome c. The expression of this gene is regulated by the tumor suppressor P53 and has been shown to be involved in P53-mediated apoptosis. Multiple alternatively spliced transcript variants, which encode different isoforms, have been reported for this gene. Product Name ...
The protein encoded by this gene belongs to the BCL2 protein family. BCL2 family members form oligomers or heterodimers and act as anti- or pro-apoptotic regulators that are involved in a wide variety of cellular activities. This protein localizes to mitochondria, and functions to induce apoptosis. It interacts with and accelerates the opening of the mitochondrial voltage-dependent anion channel, which leads to a loss in membrane potential and the release of cytochrome c. This protein also interacts with the tumor suppressor P53 after exposure to cell stress. [provided by RefSeq, Jul 2008] ...
Sugar permeation through maltoporin of Escherichia coli, a trimer protein that facilitates maltodextrin translocation across outer bacterial membranes, was investigated at the single channel level. For large sugars, such as maltohexaose, elementary e
Khandelwal and colleagues succeeded in identifying the insecticidal factor. The active component was found in a large complex normally associated with the bacterial outer membrane, and was also present in or on outer membrane vesicles (OMVs) released from the bacterial surface, says Khandelwal. They then searched through OMV components and identified a small (17 kDa) toxic protein. When purified, this protein was toxic to cultured larval cells and directly killed H. armigera larvae. Gene cloning and sequencing showed this protein is related to a class of bacterial outer membrane proteins that form protrusions, called pili or fimbriae, which often help bacteria attach to host cells during infection. Similar to pili proteins, the purified 17 kDa protein self-associated to form oligomers, each of which was connected to the next by a strand. Most importantly, the recombinant 17 kDa protein killed H. armigera larvae, demonstrating its potential as a biological control agent in a world desperately in ...
An axial flow staged zone oligomerization reaction process includes the steps of passing a hydrocarbon feedstock into the lower portion of the axial flow staged zone reactor which includes axial circulation of the hydrocarbon reaction fluid serially in each of the reaction zones, passing catalyst through a constriction zone located between successive upper and lower catalytic reaction zones which includes heat exchanging of the fluids being the constriction zone within the reactor and further includes withdrawing the oligomerized product from the top of the reactor.
Introduction. The marA, soxS, ramA, acrB and ompF genes have been studied in order to characterize mechanisms of AcrAB-TolC active efflux pumps and membrane permeability alterations that reduce fluoroquinolones susceptibility in Salmonella spp. Methods. Mutations in marA, soxS, ramA, acrB and ompF genes were detected, as well as their expression levels in presence and absence of ciprofloxacin, calculating the level of change between them by qPCR. Data were analysed by using SPSS 19.0. Results. No mutations in these genes were found, but both AcrAB-TolC regulatory genes and structural acrB gene expression were affected by ciprofloxacin in both mutant strains and wild type bacterial strains (WT ...
Simple and facilitated diffusion: Diffusion of molecules or ions through a membrane is of two types - simple and facilitated. The simple diffusion refers to the type of transfer in which the diffusing molecules or ions do not combine with the constituents of the membrane. For example, gases like oxygen, carbon dioxide etc., and water molecules diffuse readily through gas created by the random movement of fatty acyl chain of lipids. The facilitated diffusion is the movement through the membrane with the help of certain transport proteins. Membranes have several such proteins which facilitate the diffusion of solutes (Cl-, HCO3- etc.) Plasma membranes of some organisms have protein pores called, porins which are water-filled transmembrane channels.. ...
Import of porin is inhibited into tom40 mutant mitochondria. (A) Radiolabeled porin precursor (10 μl reticulocyte lysate per lane) was incubated with isolated
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Mapping the Laminin Receptor Binding Domains of Neisseria meningitidis PorA and Haemophilus influenzae OmpP2. . Biblioteca virtual para leer y descargar libros, documentos, trabajos y tesis universitarias en PDF. Material universiario, documentación y tareas realizadas por universitarios en nuestra biblioteca. Para descargar gratis y para leer online.
Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae are major bacterial agents of meningitis. They each bind the 37/67-kDa laminin receptor (LamR) via the surface protein adhesins: meningococcal PilQ and PorA, H. influenzae OmpP2 and pneumococcal CbpA. We have previously reported that a surface-exposed loop of the R2 domain of CbpA mediates LamR-binding. Here we have identified the LamR-binding regions of PorA and OmpP2. Using truncated recombinant proteins we show that binding is dependent on amino acids 171-240 and 91-99 of PorA and OmpP2, respectively, which are predicted to localize to the fourth and second surface-exposed loops, respectively, of these proteins. Synthetic peptides corresponding to the loops bound LamR and could block LamR-binding to bacterial ligands in a dose dependant manner. Meningococci expressing PorA lacking the apex of loop 4 and H. influenzae expressing OmpP2 lacking the apex of loop 2 showed significantly reduced LamR binding. Since both ...
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 ...
Xanthomonas campestris pv. campestris (Xcc) is the phytopathogen that causes black rot in crucifers. The xanthan polysaccharide and extracellular enzymes produced by this organism are virulence factors, the expression of which is upregulated by Clp (CRP-like protein) and DSF (diffusible signal factor), which is synthesized by RpfF. It is also known that biofilm formation/dispersal, regulated by the effect of controlled synthesis of DSF on cell-cell signalling, is required for virulence. Furthermore, a deficiency in DSF causes cell aggregation with concomitant production of a gum-like substance that can be dispersed by addition of DSF or digested by exogenous endo-β-1,4-mannanase expressed by Xcc. In this study, Western blotting of proteins from a mopB mutant (XcMopB) showed Xcc MopB to be the major outer-membrane protein (OMP); Xcc MopB shared over 97 % identity with homologues from other members of Xanthomonas. Similarly to the rpfF mutant, XcMopB formed aggregates with simultaneous production of a
The fucose binding lectin LecB affects biofilm formation and is involved in pathogenicity of Pseudomonas aeruginosa. LecB resides in the outer membrane and can be released specifically by treatment of an outer membrane fraction with fucose suggesting that it binds to specific ligands. Here, we report that LecB binds to the outer membrane protein OprF. In an OprF-deficient P. aeruginosa mutant, LecB is no longer detectable in the membrane but instead in the culture supernatant indicating a specific interaction between LecB and OprF.
Several properties of Haemophilus influenzae outer membrane proteins were analyzed to define related proteins in various isolates. H. influenzae type b 760705 had six major outer membrane proteins with the following characteristics. Protein a (Mr, 47,000) demonstrated heat modifiability in sodium dodecyl sulfate; its apparent molecular weight was 34,000 at temperatures below 60 degrees C. This protein was extracted from cell envelopes by using Triton X-100-10 mM MgCl2; in cell envelope preparations, the protein was degraded by trypsin. Proteins b (Mr, 41,000) and c (Mr, 40,000) were insensitive to trypsin degradation, were not heat modifiable in sodium dodecyl sulfate, and were peptidoglycan associated in 0.5% Triton X-100-0.2% sodium dodecyl sulfate. The amount of protein b was reduced in ultrasonically obtained cell envelopes. Protein d (Mr, 37,000) was heat modifiable in sodium dodecyl sulfate with an Mr of 28,000 at temperatures below 100 degrees C and was degraded by trypsin, leaving a ...
Cloning and characterization of the major outer membrane protein gene (ompH) of Pasteurella multocida X-73.: The major outer membrane protein (OmpH) of Pasteure
The susceptibility of the E. coli B strain to a variety of stressful conditions and antibiotics revealed by PM tests (Figure S3 in Additional file 1) can be explained by several observations (Figure 5). First, differences in the composition of the LPS core and expression of outer membrane proteins may influence the permeability and integrity of the cell envelope. B strains produce more OmpF porin than K-12 strains because the B genome lacks micF, which post-transcriptionally prevents production of OmpF [24]. This is further supported by the transcriptome data showing high levels of ompF expression in the B strain and high expression of ompC and ompA in the K-12 strain (Figure 4). These observations were also consistent with results of proteome analysis of the outer membrane fractions (Figure S2B in Additional file 1). Noxious agents such as antibiotics and bile acids diffuse more easily through OmpF than OmpC because the former produces a channel with a larger pore size [25]. Second, synthesis ...