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At least 91 records · Page 5Linked to original sources
PubMed1990

Comparison of nitrogen-15 and diaminopimelic acid for estimating bacterial protein synthesis of lactating cows fed diets of varying protein degradability.

Three lactating Holstein cows fitted with duodenal cannulae were fed diets containing cottonseed meal, corn gluten meal, or blood meal as protein supplements in a 3 c 3 Latin square experiment. Diets averaged 15% CP and were 60% concentrate, 31% corn silage, and 9% alfalfa hay. The flow marker was Cr2O3; the bacterial protein fraction of digesta CP was estimated by 15N (as ammonium sulfate) and diaminopimelic acid. The undegraded fraction of total feed protein entering the duodenum for respective diets was .52, .57, and .69. The 15N method was less variable than diaminopimelic acid. Based on 15N, percentage of bacterial of total protein differed among treatments (61.5, 59.4, and 55.0, respectively). Ten percent more protein entered the duodenum on blood meal than other diets, but differences were not significant. Protein sources were similar in microbial passage, but degraded protein was used most efficiently for microbial synthesis on blood meal. Incorporation of 15N consumed into bacterial protein ranged from 50 to 83% with numerically highest values on blood meal, suggesting greater efficiency of ammonia, capture. Recoveries of 15N for the 72 h as milk, feces and urine ranged from 54 to 78%.

Animal Feed↗
PubMed1989

Protein L: an immunoglobulin light chain-binding bacterial protein. Characterization of binding and physicochemical properties.

Protein L, a cell wall molecule of the bacterial species Peptostreptococcus magnus with affinity for immunoglobulin (Ig) light chains, was isolated after solubilization of the bacterial cell walls with mutanolysin or from the culture medium by a single affinity chromatography step on human IgG-Sepharose. A major protein band with an apparent molecular weight of 95,000 was obtained from both sources. The protein from the growth medium was size heterogeneous. From 1 ml of packed bacteria was prepared 0.92 mg of the mutanolysin-solubilized protein L (73% yield), whereas 4.1 mg of spontaneously released protein L (49% yield) was purified from the corresponding culture medium. The Mr of protein L was estimated to 76,000 by gel chromatography in 6 M guanidine HCl. Using this Mr value, the Stokes radius and the frictional ratio of protein L were determined to 4.74 nm and 1.70, respectively, suggesting an elongated fibrous molecule. No disulfide bond or subunit structure could be shown. The amino-terminal amino acid sequences of the whole protein and two internal non-IgG-binding tryptic fragments were determined and found to be unique. One of the tryptic fragments showed homology (40% identical residues) to a sequence within the cell wall-binding region of protein G, the Fc-binding protein of group C and G streptococci. The binding specificity of protein L was directed to the light chains of immunoglobulins; the affinity constant for polyacrylamide-coupled kappa-chains was 1.5 x 10(9) M-1 and for IgG, IgA, and IgM around 1 x 10(10) M-1. Maximal binding was achieved between pH 7 and 10. The binding to lambda-chains was too weak for determination of the affinity constant. 125I-Protein L was also shown to bind to mouse immunoglobulins. It could be used for detection of antigen-bound polyclonal and monoclonal antibodies in Western blots. This shows that the protein L/light chain reaction was not obstructed by occupation of the antigen-binding site. Finally, protein L and kappa-chains of human Ig formed precipitates upon double immunodiffusion analysis, an indication of at least two binding sites on protein L.

Amino Acid Sequence↗
PubMed1996

Bacterial protein toxins and cell vesicle trafficking.

A group of bacterial protein toxins interfere with vesicular trafficking inside cells. Clostridial neurotoxins affect mainly the highly regulated fusion of neurotransmitter- and hormone-containing vesicles with the plasma membrane. They cleave the three SNARE proteins: VAMP, SNAP-25 and syntaxin, and this selective proteolysis results in a blockade of exocytosis. The Helicobacter pylori cytotoxin is implicated in the pathogenesis of gastroduodenal ulcers. It causes a progressive and extensive vacuolation of cells followed by necrosis, after a cytotoxin-induced alteration of membrane trafficking by late endosomes. Vacuoles originate from this compartment in a rab7-dependent process and swell because they are acidic and accumulate membrane-permeant amines.

Bacterial Toxins↗
PubMed1997

The Listeria monocytogenes-secreted p60 protein is an N-end rule substrate in the cytosol of infected cells. Implications for major histocompatibility complex class I antigen processing of bacterial proteins.

Cytosolic antigen degradation is an initial step in the generation of major histocompatibility complex (MHC) class I-associated cytolytic T lymphocyte epitopes. Intracellular Listeria monocytogenes secretes p60, a murein hydrolase, into the host cell cytosol, where it is degraded by proteasomes. Roughly 3% of degraded p60 gives rise to p60 217-225, a nonamer peptide that is bound by H-2Kd MHC class I molecules. Herein, we introduce targeted deletions throughout the p60 gene to identify potential proteolytic signals within p60. Degradation of mutant forms of p60 was investigated in macrophages infected with recombinant L. monocytogenes. We found that deletions within the amino-terminal two-thirds of p60 enhanced cytosolic degradation. In contrast, truncation of the C terminus resulted in modest stabilization of p60 in the host cell cytosol. Because a protein's N-terminal amino acid can determine its rate of degradation, we mutagenized this residue in p60 into known stabilizing and destabilizing residues. Valine substitution dramatically stabilized cytosolic p60 molecules, while substitution with aspartic acid resulted in rapid degradation. The number of p60 217-225 epitopes isolated from infected cells directly correlated with the rates of p60 degradation. Our data, therefore, indicate that the N-terminal amino acid and multiple internal regions of p60 influence its stability in the cytosol of infected cells. Antigen degradation and epitope generation are linked, and different degradation signals can channel bacterial proteins into the MHC class I antigen processing pathway.

Antigen Presentation↗
PubMed1981

Effects of monensin on site and extent of whole corn digestion and bacterial protein synthesis in beef steers.

Monensin was fed at 0 and 33 ppm in a crossover trial designed to determine the effect of this compound on ruminal and postruminal utilization of a corn-based diet and bacterial protein synthesis in abomasally fistulated steers. Monensin decreased (P greater than .10) ruminal true digestion of organic matter (OMc, corrected for bacterial cell synthesis) and apparent ruminal digestion of starch by 19%, but had not effect on apparent total tract digestion of OM or starch. Apparent ruminal and total tract digestibilities of crude protein (CP) were unchanged. Monensin decreased (P greater than .07) the contribution of bacterial N to total abomasal N (52 vs 58%), and increased (P greater than .06) the contribution of ruminally undegraded feed N (46 vs 40%), but had not effect on total N or amino acids recovered from the abomasum. Efficiency of bacterial protein synthesis (grams bacterial CP/100 g ruminally digested OMc) was unchanged. Monensin decreased (P greater than .05) the fraction of bacterial N to total N digested postruminally (42 vs 50%) and increased (P greater than .05) the contribution of ruminally undegraded feed N digested postruminally (58 vs 50%). Monensin caused a greater proportion of feed N and starch to be digested in the intestines than in the rumen (with possibly greater resultant metabolic efficiency), and this may account for some of the benefits obtained from feeding this compound with high grain diets.

Abomasum↗
PubMed1993

Effects of multiplicity of infection, bacterial protein synthesis, and growth phase on adhesion to and invasion of human cell lines by Salmonella typhimurium.

Monolayers of intestine 407 (Int-407) cells were infected with the virulent Salmonella typhimurium strain C52, and the adhesion to and invasion of these cells were studied. The effects of the multiplicity of infection and growth phase of the bacteria (logarithmic versus stationary) on the interaction with eukaryotic cells were investigated. In contrast to other reports, we found no differences in the adhesive and invasive capacities of bacteria derived from logarithmic- or stationary-phase cultures. Invasion by S. typhimurium required bacterial protein synthesis and live Int-407 cells. Bacteria adhered equally well to dead or live Int-407 cells, which indicates that adhesion does not require metabolically active cells. Adhesion of S. typhimurium followed saturation kinetics, with a maximum of 10 adhesive bacteria per cell. This indicates that there is a limited number of bacterial adhesion sites (receptors) available on the surface of the host cell. Killed and live bacteria adhered equally well and competed with each other for cellular adhesion sites. This and adhesion experiments performed in the presence of chloramphenicol showed that bacterial protein synthesis is not required for adhesion. The general validity of the results obtained with S. typhimurium C52 was confirmed by comparing the invasion and adhesion data with those of the frequently used SL1344 and SR11 strains. In addition, we assayed the adhesion and invasion of S. typhimurium C52, SL1344, and SR11 and 27 S. typhimurium field isolates with Int-407, HeLa, and HEp-2 cells.

Bacterial Adhesion↗
PubMed2006

Brucella abortus rough mutants induce macrophage oncosis that requires bacterial protein synthesis and direct interaction with the macrophage.

Previous studies suggest that smooth Brucella organisms inhibit macrophage apoptosis. In contrast, necrotic cell death of macrophages infected with rough Brucella organisms in vitro has been reported, which may in part explain the failure of some rough organisms to thrive. To characterize these potential macrophage killing mechanisms, J774.A1 murine macrophages were infected with Brucella abortus S2308-derived rough mutant CA180. Electron microscopic analysis and polyethylene glycol protection assays revealed that the cells were killed as a result of necrosis and oncosis. This killing was shown to be unaffected by treatment with carbenicillin, an inhibitor of bacterial cell wall biosynthesis and, indirectly, replication. In contrast, chloramphenicol treatment of macrophages infected at multiplicities of infection exceeding 10,000 prevented cell death, despite internalization of large numbers of bacteria. Similarly, heat-killed and gentamicin-killed CA180 did not induce cytopathic effects in the macrophage. These results suggested that killing of infected host cells requires active bacterial protein synthesis. Cytochalasin D treatment revealed that internalization of the bacteria was necessary to initiate killing. Transwell experiments demonstrated that cell death is not mediated by a diffusible product, including tumor necrosis factor alpha and nitric oxide, but does require direct contact between host and pathogen. Furthermore, macrophages preinfected with B. abortus S2308 or pretreated with B. abortus O polysaccharide did not prevent rough CA180-induced cell death. In conclusion, Brucella rough mutant infection induces necrotic and oncotic macrophage cell death that requires bacterial protein synthesis and direct interaction of bacteria with the target cells.

Animals↗
PubMed1990

Demonstration of shared epitopes between bacterial proteins and HLA class-I proteins using monoclonal antibodies.

Monoclonal antibodies were used to identify the presence of epitopes on bacterial proteins which are cross-reactive with HLA-B27. Anti-HLA-B27 monoclonals, B27M2 and YE-2 reacted with a major protein of approximately 35 kDa, which was found to be OMPA. On some strains a 19 KDa protein was also seen. Anti-Shigella flexneri monoclonals were also developed which reacted with a 36 kDa protein and a 19 kDa protein. The 36 kDa protein was OMPF. These antibodies also reacted with a synthetic peptide representing amino acids 63-83 of the B*2705 sequence. These results support a potential role for molecular mimicry in the spondyloarthropathies.

Antibodies, Monoclonal↗
PubMed1997

Solution structure of the albumin-binding GA module: a versatile bacterial protein domain.

The albumin-binding GA module is found in a family of surface proteins of different bacterial species. It comprises 45 amino acid residues and represents the first known example of contemporary module shuffling. Using 1H NMR spectroscopy we have determined the solution structure of the GA module from protein PAB, a protein of the anaerobic human commensal and pathogen Peptostreptococcus magnus. This structure, the first three-dimensional structure of an albumin-binding protein domain described, was shown to be composed of a left-handed three-helix-bundle. Sequence differences between GA modules with different affinities for albumin indicated that a conserved region in the C-terminal part of the second helix and the flexible sequence between helices 2 and 3 could contribute to the albumin-binding activity. The effect on backbone amide proton exchange rates upon binding to albumin support this assumption. The GA module has a fold that is strikingly similar to the immunoglobulin-binding domains of staphylococcal protein A but it shows no resemblance to the fold shared by the immunoglobulin-binding domains of streptococcal protein G and peptostreptococcal protein L. When the gene sequences, binding properties and thermal stability of these four domains are analysed in relation to their global folds an evolutionary pattern emerges. Thus, in the evolution of novel binding properties mutations are allowed only as long as the energetically favourable global fold is maintained.

Amino Acid Sequence↗
PubMed2005

PSLpred: prediction of subcellular localization of bacterial proteins.

SUMMARY: We developed a web server PSLpred for predicting subcellular localization of gram-negative bacterial proteins with an overall accuracy of 91.2%. PSLpred is a hybrid approach-based method that integrates PSI-BLAST and three SVM modules based on compositions of residues, dipeptides and physico-chemical properties. The prediction accuracies of 90.7, 86.8, 90.3, 95.2 and 90.6% were attained for cytoplasmic, extracellular, inner-membrane, outer-membrane and periplasmic proteins, respectively. Furthermore, PSLpred was able to predict approximately 74% of sequences with an average prediction accuracy of 98% at RI = 5. AVAILABILITY: PSLpred is available at http://www.imtech.res.in/raghava/pslpred/

Algorithms↗
PubMed2001

Bacterial protein toxins inhibiting low-molecular-mass GTP-binding proteins.

The Rho GTPases, which belong to the Ras superfamily of low-molecular-mass GTP-binding proteins, are the preferred intracellular targets of bacterial protein toxins. The Rho GTPases RhoA/B/C, Rac1/2 and Cdc42 are the master regulators of the actin cytoskeleton. Clostridium difficile toxins A and B, the causative agents of the antibiotic-associated pseudomembranous colitis, are intracellularly acting cytotoxins which mono-glucosylate the Rho GTPases. Clostridium botulinum C3 toxin, which is not related to the clostridial neurotoxins, catalyses ADP-ribosylation of RhoA/B/C but not of other Rho GTPases. Glucosylation as well as ADP-ribosylation result in functional inactivation of Rho causing disassembly of the actin cytoskeleton.

Animals↗
PubMed1994

Bacterial protein toxins acting on the cell cytoskeleton.

A number of bacterial protein toxins are known to exert their cytotoxic activity via a modification of cytoskeletal components. Some toxins induce the ADP-ribosylation of actin whereas others interact with the cytoskeleton by an unknown mechanism. Understanding the mode of action of such toxins at cellular level could provide useful information on their role in vivo as virulence factors.

Actin Cytoskeleton↗
PubMed2006

Bacterial proteins and CpG-rich extrachromosomal DNA in potential cancer therapy.

Bacterial proteins such as azurin and Laz have recently been shown to enter preferentially to cancer cells and kill them by multiple mechanisms. Historically, bacterial DNA, particularly the unmethylated CpG dinucleotides, have been shown to trigger activation of specific Toll-like receptors (TLRs) in immune cells, leading to various cytokine and chemokine production that allows cancer cell death and their regression. However, the enhanced release of specific protein or extrachromosomal DNA by bacteria in response to exposure to cancer cells has not been previously demonstrated. In this review, we discuss how an opportunistic, extracellular pathogenic bacterium, Pseudomonas aeruginosa, senses the presence of cancer cells and releases a specific protein or extrachromosomal DNA with antitumor activity for inhibition of cancer cell growth.

Amino Acid Sequence↗
PubMed1994

Bacterial-protein interactions in the oral cavity.

Bacteria in the oral cavity must interact with salivary proteins if they are to survive. Such interactions can take several forms, either providing nutrients, a means of adhesion to surfaces, or resulting in aggregation or killing and, therefore, clearance of organisms. Recent work has provided an insight into the mechanisms of some of these bacterial-protein interactions, revealing complexity and diversity. For example, the interaction between a putative Streptococcus mutans adhesin, P1 (B, I/II, etc.), and a parotid glycoprotein results in adhesion when it occurs at a surface or aggregation when in solution, and different domains of P1 appear to be involved in the two processes. An alternative strategy is employed by Actinomyces viscosus, which interacts, via its type-1 fimbriae, with a proline-rich salivary protein; however, this interaction occurs only when the PRP is adsorbed to a surface. A. viscosus takes advantage of a conformational change in the PRP when it becomes surface-bound, which exposes a cryptic part of the molecule. A third, and intriguing, type of interaction is seen between various streptococci and salivary amylase. This does not result in either adherence or aggregation but provides organisms with the ability to utilize starch breakdown products for metabolism. An understanding of the mechanisms involved in bacterial-protein interactions could conceivably lead to novel methods for controlling specific pathogens, but the systems operating in the mouth are numerous, complex, and diverse.

Actinomyces↗
PubMed2005

Assimilation efficiency of Vibrio bacterial protein biomass by the flagellate Pteridomonas : assessment using flow cytometric sorting.

A flow cytometric sorting technique for direct determination of bacterial biomass assimilation by phagotrophic flagellates was developed and tested in laboratory culture experiments. Living Vibrio bacteria were quantitatively pulse-chase labelled with [(35)S]methionine tracer and fed to Pteridomonas flagellates. Flow sorting revealed that the isotopically labelled material is in either bacterial prey or flagellate predators and the egested bacterial debris contained negligible amounts of tracer. These experimental results confirm an earlier hypothesis that flagellates release metabolised bacterial proteins primarily in a dissolved form. The assimilation efficiency of the Vibrio protein biomass by Pteridomonas was low, only about 20%, independently of the amount of consumed bacterial biomass, confirming our earlier indirect estimates. Additionally, against expectations that cells decrease their metabolic activity whilst preparing for and engaged in division, we found that the precursor uptake rates by flow sorted bacterial cells at the S+G(2) cell cycle stages were constantly 1.5 times higher than those of cells at the G(1) stage.

Animals↗
PubMed2001

Green fluorescent protein--a bright idea for the study of bacterial protein localization.

Use of the green fluorescent protein (GFP) of Aequorea victoria as a reporter for protein and DNA localization has provided sensitive, new approaches for studying the organization of the bacterial cell, leading to new insights into diverse cellular processes. GFP has many characteristics that make it useful for localization studies in bacteria, primarily its ability to fluoresce when fused to target polypeptides without the addition of exogenously added substrates. As an alternative to immunofluorescence microscopy, the expression of gfp gene fusions has been used to probe the function of cellular components fundamental for DNA replication, translation, protein export, and signal transduction, that heretofore have been difficult to study in living cells. Moreover, protein and DNA localization can now be monitored in real time, revealing that several proteins important for cell division, development and sporulation are dynamically localized throughout the cell cycle. The use of additional GFP variants that permit the labeling of multiple components within the same cell, and the use of GFP for genetic screens, should continue to make this a valuable tool for addressing complex questions about the bacterial cell.

Bacteria↗