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Bernd H A Rehm

Publications and source records attributed to Bernd H A Rehm.

At least 19 recordsLinked to original sources
PubMed2007

Recombinant Escherichia coli produces tailor-made biopolyester granules for applications in fluorescence activated cell sorting: functional display of the mouse interleukin-2 and myelin oligodendrocyte glycoprotein.

BACKGROUND: Fluorescence activated cell sorting (FACS) is a powerful technique for the qualitative and quantitative detection of biomolecules used widely in both basic research and clinical diagnostic applications. Beads displaying a specific antigen are used to bind antibodies which are then fluorescently labelled using secondary antibodies. As the individual suspension bead passes through the sensing region of the FACS machine, fluorescent signals are acquired and analysed. Currently, antigens are tediously purified and chemically cross-linked to preformed beads. Purification and coupling of proteins often renders them inactive and they will not be displayed in its native configuration. As an alternative, we genetically engineered Escherichia coli to produce biopolyester (polyhdroxyalkanoate=PHA) granules displaying diagnostically relevant antigens in their native conformation and suitable for FACS analysis. RESULTS: Hybrid genes were constructed, which encode either the mouse interleukin-2 (IL2) or the myelin oligodendrocyte glycoprotein (MOG) fused via an enterokinase site providing linker region to the C terminus of the PHA granule associated protein PhaP, respectively. The hybrid genes were expressed in PHA-accumulating recombinant E. coli. MOG and IL2 fusion proteins were abundantly attached to PHA granules and were identified by MALDI-TOF/MS analysis and N terminal sequencing. A more abundant second fusion protein of either MOG or IL2 resulted from an additional N terminal fusion, which did surprisingly not interfere with attachment to PHA granule. PHA granules displaying either IL2 or MOG were used for FACS using monoclonal anti-IL2 or anti-MOG antibodies conjugated to a fluorescent dye. FACS analysis showed significant and specific binding of respective antibodies. Enterokinase treatment of IL2 displaying PHA granules enabled removal of IL2 as monitored by FACS analysis. Mice were immunized with either MOG or OVA (ovalbumin) and the respective sera were analysed using MOG-displaying PHA granules and FACS analysis showing a specific and sensitive detection of antigen-specific antibodies within a wide dynamic range. CONCLUSION: E. coli can be genetically engineered to produce PHA granules displaying correctly folded eukaryotic proteins and which can be applied as beads in FACS based diagnostics. Since PHA granule formation and protein attachment occurs in one step already inside the bacterial cell, microbial production could be a cheap and efficient alternative to commercial beads.

Animals↗
PubMed2006

Recombinant Escherichia coli strain produces a ZZ domain displaying biopolyester granules suitable for immunoglobulin G purification.

The immunoglobulin G (IgG) binding ZZ domain of protein A from Staphylococcus aureus was fused to the N terminus of the polyhydroxyalkanoate (PHA) synthase from Cupriavidus necator. The fusion protein was confirmed by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and mediated formation of ZZ domain-displaying PHA granules in recombinant Escherichia coli. The IgG binding capacity of isolated granules was assessed using enzyme-linked immunosorbent assay and could be enhanced by the overproduction of the ZZ-PHA synthase. ZZ-PHA granules enabled efficient purification of IgG from human serum.

Acyltransferases↗
PubMed2006

Bacterial alginates: from biosynthesis to applications.

Alginate is a polysaccharide belonging to the family of linear (unbranched), non-repeating copolymers, consisting of variable amounts of beta-D-mannuronic acid and its C5-epimer alpha- L-guluronic acid linked via beta-1,4-glycosidic bonds. Like DNA, alginate is a negatively charged polymer, imparting material properties ranging from viscous solutions to gel-like structures in the presence of divalent cations. Bacterial alginates are synthesized by only two bacterial genera, Pseudomonas and Azotobacter, and have been extensively studied over the last 40 years. While primarily synthesized in form of polymannuronic acid, alginate undergoes chemical modifications comprising acetylation and epimerization, which occurs during periplasmic transfer and before final export through the outer membrane. Alginate with its unique material properties and characteristics has been increasingly considered as biomaterial for medical applications. The genetic modification of alginate producing microorganisms could enable biotechnological production of new alginates with unique, tailor-made properties, suitable for medical and industrial applications.

Alginates↗
PubMed2006

Alg44, a unique protein required for alginate biosynthesis in Pseudomonas aeruginosa.

Here the putative alginate biosynthesis gene alg44 of Pseudomonas aeruginosa was functionally assigned. Non-polar isogenic alg44 deletion mutants of P. aeruginosa were generated and did neither produce alginate nor released free uronic acids. No evidence for alginate enrichment in the periplasm was obtained. Alginate production was restored by introducing only the gene alg44. PhoA fusion protein analyses suggested that Alg44 is a soluble protein localized in the periplasm. Hexahistidine-tagged Alg44 was detected by immunoblotting. The corresponding 42.6 kDa protein was purified and identified by MALDI/TOF-MS analysis. Alg44 might be directly involved in alginate polymerization presumably by exerting a regulatory function.

Alginates↗
PubMed2006

Genetics and biochemistry of polyhydroxyalkanoate granule self-assembly: The key role of polyester synthases.

PHAs (polyhydroxyalkanoates = biopolyester) composed of hydroxy fatty acids represent a rather complex class of storage polymers synthesized by various bacteria and archaea and are deposited as water-insoluble cytoplasmic nano-sized inclusions. These spherical particles are composed of a polyester core surrounded by phospholipids and proteins. The key enzymes of polyester biosynthesis and polyester particle formation are the polyester synthases, which catalyze the formation of polyesters. Various metabolic routes have been identified and established in bacteria to provide substrate for polyester synthases. Although not essential for particle formation, non-covalently attached proteins, the so-called phasins, can be found at the particle surface and are considered as structural proteins. Protein engineering of polyester synthases and phasins was used to shed light into the topology of these granule attached proteins. Biopolyesters and the respective micro-/nano-structures are currently considered as biocompatible and biodegradable biomaterials with numerous potential applications particularly in the medical field.

Acyltransferases↗
PubMed2006

In vitro alginate polymerization and the functional role of Alg8 in alginate production by Pseudomonas aeruginosa.

An enzymatic in vitro alginate polymerization assay was developed by using 14C-labeled GDP-mannuronic acid as a substrate and subcellular fractions of alginate overproducing Pseudomonas aeruginosa FRD1 as a polymerase source. The highest specific alginate polymerase activity was detected in the envelope fraction, suggesting that cytoplasmic and outer membrane proteins constitute the functional alginate polymerase complex. Accordingly, no alginate polymerase activity was detected using cytoplasmic membrane or outer membrane proteins, respectively. To determine the requirement of Alg8, which has been proposed as catalytic subunit of alginate polymerase, nonpolar isogenic alg8 knockout mutants of alginate-overproducing P. aeruginosa FRD1 and P. aeruginosa PDO300 were constructed, respectively. These mutants were deficient in alginate biosynthesis, and alginate production was restored by introducing only the alg8 gene. Surprisingly, this resulted in significant alginate overproduction of the complemented P. aeruginosa Deltaalg8 mutants compared to nonmutated strains, suggesting that Alg8 is the bottleneck in alginate biosynthesis. (1)H-NMR analysis of alginate isolated from these complemented mutants showed that the degree of acetylation increased from 4.7 to 9.3% and the guluronic acid content was reduced from 38 to 19%. Protein topology prediction indicated that Alg8 is a membrane protein. Fusion protein analysis provided evidence that Alg8 is located in the cytoplasmic membrane with a periplasmic C terminus. Subcellular fractionation suggested that the highest specific PhoA activity of Alg8-PhoA is present in the cytoplasmic membrane. A structural model of Alg8 based on the structure of SpsA from Bacillus subtilis was developed.

Alginates↗
PubMed2006

In vivo enzyme immobilization by use of engineered polyhydroxyalkanoate synthase.

This study demonstrated that engineered polyhydroxyalkanoate (PHA) synthases can be employed as molecular tools to covalently immobilize enzymes at the PHA granule surface. The beta-galactosidase was fused to the N terminus of the class II PHA synthase from Pseudomonas aeruginosa. The open reading frame was confirmed to encode the complete fusion protein by T7 promoter-dependent overexpression. Restoration of PHA biosynthesis in the PHA-negative mutant of P. aeruginosa PAO1 showed a PHA synthase function of the fusion protein. PHA granules were isolated and showed beta-galactosidase activity. PHA granule attached proteins were analyzed and confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization-time of flight mass spectrometry. Surprisingly, the beta-galactosidase-PHA synthase fusion protein was detectable at a high copy number at the PHA granule, compared with PHA synthase alone, which was barely detectable at PHA granules. Localization of the beta-galactosidase at the PHA granule surface was confirmed by enzyme-linked immunosorbent assay using anti-beta-galactosidase antibodies. Treatment of these beta-galactosidase-PHA granules with urea suggested a covalent binding of the beta-galactosidase-PHA synthase to the PHA granule. The immobilized beta-galactosidase was enzymologically characterized, suggesting a Michaelis-Menten reaction kinetics. A Km of 630 microM and a Vmax of 17.6 nmol/min for orthonitrophenyl-beta-D-galactopyranoside as a substrate was obtained. The immobilized beta-galactosidase was stable for at least several months under various storage conditions. This study demonstrated that protein engineering of PHA synthase enables the manufacture of PHA granules with covalently attached enzymes, suggesting an application in recycling of biocatalysts, such as in fine-chemical production.

Acyltransferases↗
PubMed2006

PslD is a secreted protein required for biofilm formation by Pseudomonas aeruginosa.

The function of pslD, which is part of the psl operon from Pseudomonas aeruginosa, was investigated in this study. The psl operon is involved in exopolysaccharide biosynthesis and biofilm formation. An isogenic marker-free pslD deletion mutant of P. aeruginosa PAO1 which was deficient in the formation of differentiated biofilms was generated. Expression of only the pslD gene coding region restored the wild-type phenotype. A C-terminal, hexahistidine tag fusion enabled the identification of PslD. LacZ and PhoA translational fusions with PslD indicated that PslD is a secreted protein required for biofilm formation, presumably via its role in exopolysaccharide export.

Bacterial Outer Membrane Proteins↗
PubMed2005

M2000: a revolution in pharmacology.

BACKGROUND: The tolerability and the anti-inflammatory and immunosuppressive properties of a novel designed non-steroidal anti-inflammatory drug, M2000 (beta-D-mannuronic acid), were investigated in various experimental models. MATERIAL/METHODS: The anti-inflammatory and immunosuppressive properties of M2000 were tested in experimental models of rheumatoid arthritis (AIA) and multiple sclerosis (EAE). Its therapeutic potency on kidney diseases was studied using experimental models of nephrosis and immune complex glomerulonephritis (ICG). Biocompatibility and pharmacotoxicology assessment of M2000 was carried out using a fibrosarcoma cell line, zymography, and serum and urine determinants. RESULTS: Data showed that oral and/or i.p. administration of M2000 significantly reduces paw edema and histopathological parameters in arthritic rats. The immunosuppressive property of M2000 could significantly diminish clinical signs and histological erosions in the EAE model. Lymph node cell proliferation assay in EAE confirmed the immunosuppressive efficacy of the tested drug. Our findings in ICG and experimental nephrosis showed that M2000 enables a significant decrease in proteinuria, BUN, serum creatinine and cholesterol, as well as glomerular lesion in M2000-treated rats. Moreover, this drug inhibited MMP-2 activity. The pharmacotoxicology study showed that M2000 is the safest anti-inflammatory and immunosuppressive drug in comparison with dexamethasone and conventional NSAIDs tested. Additionally, M2000 had no ulcerogenic effect on the rat stomach. CONCLUSIONS: M2000 is the first novel designed NSAID with the lowest molecular weight, no gastro-nephrotoxicity, and therapeutic effects in glomerulonephritis and nephrosis and could be strongly recommended on an extensive scale as the safest drug for decreasing anti-inflammatory reactions.

Animals↗
PubMed2005

In vivo monitoring of PHA granule formation using GFP-labeled PHA synthases.

For the first time a functional protein was fused to a PHA synthase resulting in PHA granule formation and display of the respective function at the PHA granule surface. The GFP reporter protein was N-terminally fused to the class I PHA synthase of Cupriavidus necator (PhaC) and the class II PHA synthase of Pseudomonas aeruginosa PAO1 (PhaC1), respectively, while maintaining PHA synthase activity and PHA granule formation. Fluorescence microscopy studies of GFP-PHA synthase attached to emerging PHA granules indicated that emerging PHA granules locate to cell poles and to midcell representing the future cell poles. A rapid oscillating movement of GFP-PHA synthase foci from pole to pole was observed. In cell division impaired Escherichia coli, PHA granules were localized between nucleoids at regular spacing suggesting that nucleoid occlusion occurred. Accordingly, anucleate regions of the E. coli mukB mutant showed no regular spacing, but PHA granules with twofold increased diameter were formed. First evidence was provided that the cell division and the localization of GFP-PHA synthase foci are in vivo co-located.

Acyltransferases↗
PubMed2005

Nitrogen-dependent regulation of medium-chain length polyhydroxyalkanoate biosynthesis genes in pseudomonads.

Comparative transcriptional analysis of polyhdroxyalkanoate (PHA) biosynthesis genes with wild type strains and mutants, which lack the intact alternative sigma factor gene rpoN, was performed using semi-quantitative RT-PCR. In Pseudomonas putida and Pseudomonas aeruginosa, phaI and phaF were co-transcribed. PhaF was a negative regulator of transcription of PHA synthase gene phaC1 but did not serve as auto-repressor. However, the alternative sigma factor RpoN is suggested as negative regulator of phaF transcription. In P. putida, phaI-phaF transcription is strongly dependent on nitrogen availability and PHA accumulation, whereas phaF transcription is not. These data suggested a differential regulation of phaF and phaIF. The phaC1 gene transcription occurred almost independently by of RpoN or nitrogen availability in both pseudomonads.

Bacterial Proteins↗
PubMed2005

Treatment of experimental immune complex glomerulonephritis by sodium alginate.

We have studied the therapeutic efficacy of the sodium alginate in experimental immune complex glomerulonephritis. Bovine serum albumin (BSA) nephritis was induced in rats by a subcutaneous immunization and daily intravenous administration of BSA. Sodium alginate at two different doses (25 and 50 mg/kg) was administered intraperitoneally at regular 72-h intervals for 6 weeks. Onset of treatment was day 42. Urinary protein was measured weekly and serum anti-BSA antibody was assessed by ELISA method at different intervals. Animals were euthanized at the 12th experimental week and blood samples and kidney specimens were obtained. BUN, serum creatinine and serum cholesterol and triglyceride were measured at the time of sacrifice. Kidney specimens were processed for light and immunofluorescent microscopic examination. The tolerability and inhibitory effect of LVA on matrix metalloproteinase 2 (MMP-2) were tested using WEHI-164 cell line and zymography method. Results of this experiment showed that treatment with sodium alginate could significantly reduce the urinary protein excretion and serum creatinine in treated rats vs. nontreated controls. Anti-BSA antibody titers were lower in treated rats than in controls at the 12th week post-immunization. There was no significant difference in the level of BUN and serum lipids between two groups. Whereas, glomerular hypercellularity, PMN infiltration and glomerular deposition of BSA were less intense in treated rats vs. controls. Moreover, in vitro examinations revealed that treatment with LVA, as a very safe agent could diminish MMP-2 activity. These results suggest that treatment with sodium alginate as a new immunosuppressive agent can reduce proteinuria, inhibit MMP-2 activity and suppress the antibody production as well as the development of glomerular lesions in a rat model of immune complex glomerulonephritis.

Alginates↗
PubMed2005

Novel immunosuppressive therapy by M2000 in experimental multiple sclerosis.

The therapeutic potency of M2000 (beta-D-mannuronic acid), a novel designed nonsteroidal anti-inflammatory drug with immunosuppressive property in T-cell-mediated autoimmune disease, was tested. The influence of M2000 on myelin basic protein (MBP)-induced experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, was assessed. M2000 at two doses, 40 and 80 mg/kg/day, was administered intraperitoneally (i.p.) to prevention and treatment groups, respectively. Onset of i.p. injections of M2000 to prophylactic and therapeutic groups was day-1 and day-7 postimmunization. The WEHI-164 cell line was used for assaying the tolerability against M2000. The results of this experiment showed that the treatment of EAE with M2000 could significantly suppress disease development both prophylactically and therapeutically; the onset and symptoms of EAE in Lewis rats could be suppressed following the administration of M2000. Clinical improvement was accompanied by a marked decrease in mean numbers of vessels with perivascular cellular infiltration in M2000-treated rats compared with nontreated control. Disease suppression was associated with a marked suppression of MBP-specific T-cell reactivity in vitro, without any evidence for a generalized impairment of T-cell activity. Moreover, M2000 also showed a very high tolerability compared with certain steroidal and nonsteroidal anti-inflammatory drugs. Collectively, our data suggest that M2000 may provide a novel therapeutic option for T-cell-mediated autoimmune diseases in animal models and possibly in humans.

Animals↗
PubMed2005

Expression of the psl operon in Pseudomonas aeruginosa PAO1 biofilms: PslA performs an essential function in biofilm formation.

The psl gene cluster, comprising 15 cotranscribed genes from Pseudomonas aeruginosa, was recently identified as being involved in exopolysaccharide biosynthesis and biofilm formation. In this study, we investigated the regulation of the psl gene cluster and the function of the first gene in this cluster, the pslA gene. PslA shows strong similarities to UDP-glucose lipid carriers. An isogenic marker-free pslA deletion mutant of P. aeruginosa PAO1 deficient in attachment and biofilm formation was used for complementation studies. The expression of only the pslA gene, comprising a coding region of 1,437 bp, restored the biofilm-forming phenotype of the wild type, indicating that PslA is required for biofilm formation by nonmucoid P. aeruginosa. The promoter region of the psl gene cluster, which encodes PslA-PslO, was identified by rapid amplification of cDNA 5' ends. Promoter assays using transcriptional fusions to lacZ and gfp indicated a constitutive expression of the psl cluster in planktonic cells and a highly regulated and localized expression in biofilms, respectively. Expression of the psl cluster in biofilms was almost exclusively found in the centers of microcolonies, as revealed by confocal laser scanning microscopy. These data suggest that constitutive expression of the psl operon enables efficient attachment to surfaces and that regulated localized psl operon expression is required for biofilm differentiation.

Bacterial Proteins↗
PubMed2004

Chemopreventive effect of M2000, a new anti-inflammatory agent.

BACKGROUND: An emerging body of literature has recently defined a reduced risk of cancer following the use of nonsteroidal anti-inflammatory drugs (NSAIDs), which are generally able to exert an apoptotic property and inhibitory effects on the activity and/or expression of matrix metalloproteinases (MMPs). This study was undertaken to explore the role of a newly designed NSAID, M2000 (C6H10O7), as an anti-inflammatory drug in chemoprevention therapy under in vitro conditions. MATERIAL/METHODS: The influence of M2000 on a fibrosarcoma cell line (WEHI-164) was investigated using an in vitro cytotoxicity assay, terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay to assess apoptosis, and gelatin zymography for evaluating the activity of matrix metalloproteinase 2 (MMP-2). RESULTS: Cytotoxicity analysis of M2000 showed a much higher tolerability than the other tested drugs (diclofenac, piroxicam, and dexamethasone) in that it showed no cytotoxic effect compared with them. The dose-dependent inhibitory effect of M2000 at concentrations of 20, 40, 80, and 200 microg/ml was significantly greater than that of dexamethasone and of piroxicam at a concentration of 200 microg/ml, whereas the inhibitory activity of M2000 paralleled diclofenac at doses of 10, 20, 40, and 200 microg/ml. Moreover, the apoptotic efficacy of M2000 was similar to that of dexamethasone. CONCLUSIONS: Based on our data, the induction of apoptosis together with MMP-2 inhibition could be indicative of a chemopreventive property of M2000. Thus this novel NSAID might be considered as a chemopreventive drug in the potential prevention and treatment of cancer and in inhibition of the angiopathogenic process.

Animals↗
PubMed2004

Regulation of polyhydroxyalkanoate biosynthesis in Pseudomonas putida and Pseudomonas aeruginosa.

Regulation of medium-chain-length polyhydroxyalkanoate biosynthesis in Pseudomonas aeruginosa and Pseudomonas putida was studied conducting PHA accumulation experiments and transcriptional analysis of PHA biosynthesis genes with wild type strains and rpoN-negative mutants. In P. putida PHA accumulation was RpoN-independent, whereas in P. aeruginosa PHA accumulation was RpoN-dependent. Transcriptional analysis applying reverse transcriptase-polymerase chain reaction showed strong induction of phaG, encoding the transacylase, under nitrogen starvation in P. putida KT2440 and the respective rpoN-negative mutant, indicating an RpoN-independent regulation of phaG. No transcription of phaG and no PHA accumulation was detected in the rpoN-negative mutant of P. aeruginosa neither from gluconate nor from octanoate as carbon source. Alginate-overproducing mutant P. aeruginosa FRD1 showed strongly decreased PHA accumulation from gluconate but no difference in phaC1 (encoding the PHA synthase) transcription, indicating that alginate biosynthesis competes with PHA biosynthesis regarding acetyl-CoA as precursor for both biopolymers. Transcription of phaF and phaI-F was nitrogen independent.

Acetyl Coenzyme A↗
PubMed2004

M-2000, as a new anti-inflammatory molecule in treatment of experimental nephrosis.

The therapeutic effect of M-2000 (C6H10O7) molecule was tested in Adriamycin-induced nephropathy. To induce experimental nephrosis, Adriamycin was given once by a single intravenous injection (7.5 mg/kg) through the tail vein. Six days after injection of Adriamycin, therapeutic protocol was developed by intraperitoneally (i.p) administration of 30 mg/kg M-2000 solution. Total of i.p. injections were 14, in which five injections were made every day and nine injections were carried out at regular 48-h intervals. Therapeutic protocol was terminated on day 28 and animals were killed on day 43. The treated patient rats showed a significant reduction in proteinuria, BUN, serum creatinine and serum cholesterol, as well as, administration of M-2000 could significantly diminish the serum level of interleukin-6 (IL-6) in treated animals compared to non-treated controls. Moreover, treatment with M-2000 significantly reduced number of glomerular leukocytes, Hypercellularity and hydropic change in capillary network within the renal cortex and decreased tubular casts. These data suggest that M-2000 therapy can ameliorate proteinuria, and suppress the progression of glomerular lesions in experimental model of nephrosis.

Animals↗