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Biomedical subjects

M Sarvas

Publications and source records attributed to M Sarvas.

At least 55 records · Page 3Linked to original sources
PubMed1992

The class 1 outer membrane protein of Neisseria meningitidis produced in Bacillus subtilis can give rise to protective immunity.

The class 1 outer membrane protein of Neisseria meningitidis B:15:P1.7,16 was expressed in Bacillus subtilis in high yield as intracellular aggregates. These were easy to isolate and the protein (called BacP1) could be solubilized under denaturing conditions. Sera of mice immunized with thus-solubilized BacP1 contained high titres of antibodies that reacted with the class 1 protein of the meningococcal envelope in immunoblots but did not react with native meningococcal envelope in enzyme immunoassays (EIA) or with intact meningococci in bactericidal assays. However, when the BacP1 protein was complexed with heterologous (Salmonella) lipopolysaccharide, the ensuing sera reacted with meningococcal envelope preparations in both EIA and immunoblots, showed subtype-specific bactericidal activity, and were protective in an infant rat meningitis model.

Amino Acid Sequence↗
PubMed1992

Secretion of the Escherichia coli outer membrane proteins OmpA and OmpF in Bacillus subtilis is blocked at an early intracellular step.

When the genes coding for the outer membrane (OM) proteins OmpA and OmpF of Escherichia coli are fused to a signal sequence of a bacillar exoenzyme and expressed in Bacillus subtilis they remain cell-bound and the signal sequence is not cleaved. To identify the step of arrest in the export of these proteins we studied their accessibility to protease applied to intact protoplasts; they remained resistant indicating fully intracellular localization. Both proteins appeared associated with the cell membranes in sedimentation and flotation centrifugation experiments. However, OmpA and OmpF proteins synthesized in B. subtilis without a signal sequence were similarly associated with membranes in centrifugation experiments whereas electron microscopy showed the presence of intracytoplasmic inclusion bodies not obviously attached to the cytoplasmic membrane. We conclude that OmpA and OmpF proteins even when provided with a functional signal sequence do not enter the export pathway in B. subtilis, probably owing to lack of a specific export component in B. subtilis.

Amino Acid Sequence↗
PubMed1991

High level production of Escherichia coli outer membrane proteins OmpA and OmpF intracellularly in Bacillus subtilis.

A high yield of Escherichia coli outer membrane proteins OmpA (about 200 mg/l) and OmpF (about 100 mg/l) was obtained in Bacillus subtilis when produced intracellularly. The yield was more than 100-fold higher than the yield of these proteins by a similar vector containing the complete signal sequence of alpha-amylase of B. amyloliquefaciens. Both proteins isolated after breakage of the B. subtilis cells by low-speed centrifugation were about 70% pure and could be solubilized by Sarkosyl, SDS and guanidine hydrochloride.

Amino Acid Sequence↗
PubMed1991

Class-3 porin protein of Neisseria meningitidis: cloning and structure of the gene.

The gene coding for the class-3 protein of Neisseria meningitidis was cloned and sequenced. The deduced amino acid (aa) sequence was highly homologous (50-78%) to those of other neisserial porin proteins. Alignment of the aa sequence of five neisserial porin proteins pinpointed several regions of identity or near identity. These are assumed to be membrane-spanning beta-strands. A comparison of the homologies between these neisserial porins showed that the class-3 protein is most closely related to the Neisseria gonorrhoeae P1A protein.

Amino Acid Sequence↗
PubMed1991

The 20 kDa C-terminally truncated form of pertussis toxin subunit S1 secreted from Bacillus subtilis.

The subunit S1 of pertussis toxin (PT) was purified as the recombinant product BacS1 from the culture supernatant of a Bacillus subtilis strain containing a secretion vector with a DNA fragment coding for the mature subunit S1 inserted downstream of the signal sequence of the alpha-amylase gene. The method of purification was successive ion exchange and adsorption chromatography. BacS1 occurred in two forms (28 and 20 kDa) of which the truncated 20-kDa peptide was the main one in the supernatant. The truncated BacS1 was purified and shown to have the same NH2-terminus as the full-size (28 kDa) BacS1. It was also enzymatically active indicating correct conformation. The truncated BacS1 was also shown to elicit neutralizing and protective antibodies when injected into mice or rabbits.

Amino Acid Sequence↗
PubMed1991

A gene (prsA) of Bacillus subtilis involved in a novel, late stage of protein export.

A gene locus of Bacillus subtilis identified by mutations (prs) conferring a defect in protein secretion was cloned from a lambdaGEM-11 expression library. The sites of three closely linked prs mutations (prs-3, prs-29 and prs-40) were found to reside in a 5.3 kb DNA fragment, which also complemented the secretion defect in prs-3 and prs-29 mutants. Partial sequencing of the fragment showed that these three mutations affect one distinct gene (prsA) encoding a putative protein of 292 amino acids (33 kDa). Sequence analysis indicated the PrsA protein to be a lipoprotein located outside the cytoplasmic membrane. Thirty percent identity was shown to the PrtM protein of Lactococcus lactis, which is involved in the maturation of an exported proteinase. The phenotypes of prsA mutants and the structural similarity of PrsA with PrtM suggest that PrsA may have a novel function at a late phase in protein export.

Amino Acid Sequence↗
PubMed1990

Production and secretion of pertussis toxin subunits in Bacillus subtilis.

Pertussis toxin (PT) is a major component of today's acellular whooping cough vaccines. The use of acellular vaccines is predicted to increase sharply in the near future. There is therefore a need to produce PT in a way that makes its purification as easy as possible. Our approach was to express all five PT subunits individually in Bacillus subtilis. We have used vectors containing the promoter and signal sequences of the alpha-amylase gene of Bacillus amyloliquefaciens followed by an insert encoding the appropriate PT-subunit. All PT-subunits were secreted and found in the culture supernatant. The level of expression varied considerably: S1 and S5 were produced in large quantities whereas much smaller amounts of S2, S3 and S4 were found. The subunits were also present in the membrane fraction of the respective strains.

Amino Acid Sequence↗
PubMed1990

Expression of pertussis toxin subunit S4 as an intracytoplasmic protein in Bacillus subtilis.

The expression and secretion of pertussis toxin subunits S1 to S5 in Bacillus subtilis by the aid of a bacillary signal sequence has been reported. While secretion of subunit S1 was high, that of others was low. Ways have now been explored to improve the yield, using S4 as an example. The addition of a protease inhibitor was found to increase the amount of S4 in the culture supernatant, but the final amount was still much below that of S1. However, intracellular expression of S4 gave a high yield (500 mg l-1) and the aggregated protein could easily be isolated in a few simple steps.

Amino Acid Sequence↗
PubMed1990

A strong antibody response to the periplasmic C-terminal domain of the OmpA protein of Escherichia coli is produced by immunization with purified OmpA or with whole E. coli or Salmonella typhimurium bacteria.

We produced in Bacillus subtilis the complete, as well as the N-terminal two-thirds, OmpA protein of Escherichia coli (called here Bac-OmpA and Bac-OmpA-dN, respectively). These Bac-OmpA proteins were used to examine the immunological properties of different parts of OmpA, free of lipopolysaccharide and other components of the outer membrane. The full-length Bac-OmpA was indistinguishable from the authentic protein isolated from E. coli (Coli-OmpA) both as immunogen and as antigen in enzyme immunoassay (EIA). The N-terminal Bac-OmpA-dN was a poor immunogen which gave rise to significantly lower titers of anti-OmpA antibody than did the full-length OmpA preparations. When used as an antigen in EIA, the Bac-OmpA-dN detected anti-OmpA antibody in serum samples from animals immunized with the full-length OmpA much less efficiently than did either Bac-OmpA or Coli-OmpA. The periplasmic C-terminal domain therefore appears to be an immunodominant epitope of the purified OmpA protein. Also, when rabbits and mice were immunized with intact, live or dead E. coli, the antibody response detected by EIA with the full-length protein, Bac-OmpA, was much stronger than that detected with the N-terminal two-thirds, Bac-OmpA-dN. Similar results were obtained with the OmpA of Salmonella typhimurium. Because the ompA gene of enterobacteria is highly conserved, the Bac-OmpA might be useful as a group-specific EIA antigen to diagnose diseases caused by members of the family Enterobacteriaceae.

Antibodies, Bacterial↗
PubMed1989

Production of pneumolysin, a pneumococcal toxin, in Bacillus subtilis.

We have expressed the pneumolysin gene of Streptococcus pneumoniae in Bacillus subtilis, both from its own promoter and as a fusion protein. The level of expression of pneumolysin from its own promoter was low. The protein produced was hemolytically active. A higher level of expression (about 10 micrograms/ml of culture) was achieved when either one of two C-terminal fragments (corresponding to amino acids 265-471 and 55-471, respectively) or the entire coding part of the pneumolysin gene were fused to the promoter and signal sequence-coding region of the alpha-amylase gene of Bacillus amyloliquefaciens. The C-terminal fusion peptides reacted with anti-pneumolysin serum, but were not hemolytically active. In both cases most of the peptide remained cell-associated. When the entire pneumolysin gene was fused to the signal sequence, a hemolytically active form of pneumolysin could be detected, and most of the product was found in a processed form in the culture supernatant. The full-length pneumolysin secreted from B. subtilis was partially purified and used as antigen in an enzyme immunoassay with rabbit anti-pneumolysin serum.

Bacillus subtilis↗
PubMed1989

Membrane proteins of Francisella tularensis LVS differ in ability to induce proliferation of lymphocytes from tularemia-vaccinated individuals.

T lymphocyte-mediated immunity is important for resistance to Francisella tularensis. To characterize the specificity of this immunity, we used membrane proteins and two lipopolysaccharide (LPS) preparations. Both membrane proteins were heat-modifiable, as indicated by their migration in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). One had an apparent molecular mass (Mm) of 120 kilodaltons (kDa) when solubilized in the SDS buffer at room temperature, but 17 kDa after heating. The respective values for the other protein were 35 kDa before and 40 kDa after heating. Both proteins were purified by a preparative SDS-PAGE. The LPS-containing preparations were isolated by aqueous phenol (WP) or PCP (phenol-chloroform-petroleum ether) extraction (LPS-R), and rendered protein-free by treatment with proteinase K. Lymphocytes from nine subjects immunized with a live tularemia vaccine from one to three years earlier responded specifically to both an F. tularensis whole cell antigen and the 17 kDa protein in the lymphocyte blast transformation test. By contrast, the 40 kDa protein and the two LPS preparations did not stimulate any detectable lymphocyte proliferation.

Adult↗
PubMed1989

Antibody production to a meningococcal outer membrane protein cloned into liv Salmonella typhimurium aroA vaccine strain.

We cloned a 28 kDa outer membrane protein (OMP) of Neisseria meningitidis group B into a live Salmonella typhimurium aroA vaccine strain SL3261. The cloned 28 kDa protein was produced in large amounts in the S. typhimurium transformant SH8182 and located in the outer membrane. A mouse-passaged derivative of SH8182 was used as a live vaccine to immunize mice; with antibiotic pressure the strain survived in the mice as well as the parent strain SL3261 and maintained the plasmid carrying the gene encoding the 28 kDa OMP. The mice produced a high titer of antibodies to the 28 kDa OMP, showing that it had been effectively presented to the immune system. The hyperimmune mouse serum bound in an enzyme immunoassay to whole cells of E. coli and group B meningococci expressing the 28 kDa OMP, but its bactericidal activity towards the meningococci was marginal. In a passive protection study, the antiserum did not protect infant rats from meningococcal infection. The results indicate that the antibodies elicited did not bind to intact meningococcal cells, possibly because of inaccessibility of the 28 kDa OMP.

Animals↗
PubMed1988

Mutants of Bacillus subtilis defective in protein export.

We have isolated a set of strains with mutations (designated prs) that decrease secretion of alpha-amylase and have a pleiotropic effect on secretion of other exoproteins. The seven mutants were selected in a strain of Bacillus subtilis which overproduces alpha-amylase due to the presence of an alpha-amylase gene on a multicopy plasmid. The mutations were mapped to four different chromosomal loci. The phenotype of the mutants, especially their pleiotropic effects and the accumulation of alpha-amylase precursor, indicated that they have defects in the mechanism of protein export. Double mutants with certain pairwise combinations of mutations in different loci had additive effects on secretion, suggesting that these prs genes encode different components of the secretion pathway.

Bacillus subtilis↗
PubMed1987

Analysis of polyamines as their dabsyl derivatives by reversed-phase high-performance liquid chromatography.

The polyamines putrescine, cadaverine, spermidine, and spermine and the corresponding mono-N-acetylpolyamines can be separated as their dimethylaminoazobenzenesulfonyl derivatives in a single analysis in less than 22 min. The method employs reversed-phase high-performance liquid chromatography (Spherisorb S5 ODS2 column) with an acetonitrile/acetate buffer gradient elution system and detection in the visible (436 nm) region. The detection limit for a single dimethylaminoazobenzenesulfonylpolyamine is less than 2 pmol.

Cadaverine↗
PubMed1987

Cloning of an outer membrane protein of Neisseria meningitidis in Escherichia coli.

A gene bank of chromosomal DNA of Neisseria meningitidis group B was constructed in phage lambda EMBL3, and screened by rabbit polyclonal antibodies to major outer membrane (OM) proteins of the meningococcus. Several clones expressing a 28 kDa protein were found. The gene coding for the 28 kDa protein was subcloned into plasmid pUC18 in Escherichia coli. The protein was expressed in E. coli and located in the OM. Rabbit antibodies were raised to the 28 kDa protein purified from E. coli and used to localize the protein in the meningococcus. The antiserum recognized a minor protein of similar electrophoretic mobility in the outer membrane complex (OMC) of the meningococcus. The 28 kDa protein was found to be common to different Neisseria species; it was expressed by both pathogenic and nonpathogenic Neisseria.

Bacterial Outer Membrane Proteins↗
PubMed1987

Expression and secretion of pertussis toxin subunit S1 in Bacillus subtilis.

Pertussis toxin (PT) is an important virulence determinant of Bordetella pertussis and one of the major protective antigens against whooping cough. The genes coding for PT have recently been cloned, but attempts to express them in Escherichia coli have been unsuccessful. We therefore explored the possibility of expressing these genes in Bacilius subtilis for which efficient vectors are available. The lack of endotoxin in the Gram-positive Bacillus might be an additional advantage for the production of a vaccine component. A DNA fragment coding for S1, one of the subunits of pertussis toxin, was inserted into an alpha-amylase secretion vector and the recombinant plasmid was introduced into B. subtilis. This resulted in high expression of S1, most of which was secreted and therefore found in the culture supernatant. This supernatant had ADP-ribosylating activity similar to that of PT. Western blot with antiserum to B. pertussis holotoxin showed several proteins ranging in size from 28 kDa to 20 kDa reacting in specific manner. About 10% of the protein recognized by the antiserum was of the size expected for native-size S1. The total amount of S1 proteins (full size and truncated) in the culture supernatant was about 100 mg/l. S1 protein made in B. subtilis was partially purified using chromatography with P-cellulose and Blue Sepharose. This preparation was used to immunize rabbits; the immune serum thus obtained recognized subunit S1 of native pertussis toxin.

Amino Acid Sequence↗
PubMed1986

Amino-terminal heterogeneity of E. coli TEM-beta-lactamase secreted from Bacillus subtilis.

E. coli TEM-beta-lactamase, secreted from Bacillus subtilis after transformation with three different hybrid plasmids, was purified and subjected to direct amino-terminal sequence analysis. The results show that the signal sequence cleavage site varies depending on the hybrid plasmid construction and cannot be exactly predicted from the DNA sequences. The results are of general interest if recombinant DNA technology is used to synthesize, e.g. pharmaceutical products where the preservation of the authentic amino-terminal structure is highly desirable.

Amino Acid Sequence↗