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PubMed1993

Staphylococcal enterotoxin type A internal deletion mutants: serological activity and induction of T-cell proliferation.

Previous findings indicate that the N-terminal region of staphylococcal enterotoxin type A (SEA) is required for its ability to induce T-cell proliferation. To better localize internal peptides of SEA that are important for induction of murine T-cell proliferation, SEA mutants that had internal deletions in their N-terminal third were constructed. A series of unique restriction enzyme sites were first engineered into sea; only one of these changes resulted in an amino acid substitution (the aspartic acid residue at position 60 of mature SEA was changed to a glycine [D60G]). Because the D60G substitution had no discernible effect on serological or biological activity, the sea allele encoding this mutant SEA was used to construct a panel of mutant SEAs lacking residues 3 to 17, 19 to 23, 24 to 28, 29 to 49, 50 to 55, 56 to 59, 61 to 73, 68 to 74, or 74 to 85. Recombinant plasmids with the desired mutations were constructed in Escherichia coli and transferred to Staphylococcus aureus. Staphylococcal culture supernatants containing the mutant SEAs were examined. Western immunoblot analysis with polyclonal anti-SEA antiserum revealed that each of the recombinant S. aureus strains produced a mutant SEA of the predicted size. All the mutant SEAs exhibited increased sensitivity to monkey stomach lavage fluid in vitro, which is consistent with these mutants having conformations unlike that of wild-type SEA or the SEA D60G mutant. In general, deletion of internal peptides had a deleterious effect on the ability to induce T-cell proliferation; only SEA mutants lacking either residues 3 to 17 or 56 to 59 consistently produced a statistically significant increase in the incorporation of [3H]thymidine. In the course of this work, two monoclonal antibodies that had different requirements for binding to SEA in Western blots were identified. The epitope for one monoclonal antibody was contained within residues 108 to 230 of mature SEA. Binding of the other monoclonal antibody to SEA appeared to be dependent on the conformation of SEA.

Amino Acid Sequence↗
PubMed1993

Recombinant human hepatitis B virus reverse transcriptase is active in the absence of the nucleocapsid or the viral replication origin, DR1.

The double-stranded DNA genome of hepatitis B virus (HBV) is reverse transcribed from the viral pregenome RNA template by a virally encoded reverse transcriptase enzyme (RT) that possesses both priming and elongation activities. Prior efforts have failed to express an active form of HBV RT outside the nucleocapsid in animal cells or to release it from viral nucleocapsids, thus restricting the characterization of this important enzyme. Here, we have engineered epitope-tagged HBV RT proteins and expressed them in Xenopus oocytes via a synthetic RT mRNA which does not include the viral capsid protein or the known initiation site for viral DNA synthesis, DR1. We demonstrate the production of an immunoprecipitable 96-kDa HBV RT protein and show, using a simple in vitro RT assay, that oocyte lysates containing this protein possess an activity that (i) catalyzes an RNA-dependent deoxynucleotide triphosphate polymerization reaction by using an as-yet-unidentified RNA template and (ii) is sensitive to the RT inhibitors actinomycin D and phosphonoformate. Experiments with the chain terminator ddATP suggest that a significant amount of chain elongation occurs in our in vitro reaction. Electrophoretic analysis reveals a heterogeneous array of RT reaction products with sizes ranging from about 100 bases to far larger than that of the input RT mRNA. These products appear to contain covalently bound protein, consistent with the notion that the RT protein may have primed their synthesis. We conclude that HBV RT activity can be uncoupled from both the nucleocapsid and the replication origin, DR1. Our results raise the possibility that unless HBV employs novel mechanisms to regulate its constitutively active RT, cellular RNAs may be reverse transcribed during HBV infection, with potential implications for the development of HBV-related liver cancer. The use of the oocyte system should facilitate studies of HBV RT, including the development of HBV RT inhibitors for antiviral therapy.

Amino Acid Sequence↗
PubMed2005

Rapid and efficient subcloning of DNA without dephosphorylation or gel electrophoresis.

Conventional subcloning into plasmid vectors often involves dephosphorylation, gel electrophoresis, DNA extraction, and purification to isolate the target insert and the cleaved plasmid. This is not only time-consuming but very often problematic. We have developed strategies that can circumvent these steps by mixing digested donor and recipient plasmids together for ligation. These strategies capitalizes on: (1) the ability to enhance the ligation efficiency of desired DNA fragments into the target vector by the generation and removal of small (< 50 bp) fragments from nontarget DNA using peripheral restriction sites and spin column technology and (2) the elimination of undesired ligation products after ligation by using the Lac Z gene, differences in antibiotic resistance among plasmid vectors, and unique restriction sites situated in nontarget DNA fragments.

Chromatography↗
PubMed2005

Current and emerging therapies for the lysosomal storage disorders.

Targeted treatments for the lysosomal storage disorders (LSDs), in the form of enzyme replacement and/or substrate depletion, have been shown to be relatively safe and effective in reversing core disease features in selected clinical subtypes (including Gaucher disease types I and III, Fabry disease and the Hurler-Scheie syndrome). These approaches have expanded the therapeutic options available to patients with rare genetic disorders, beyond palliative measures (such as liver or kidney transplantation for end-organ failure) and cellular replacement through bone marrow transplantation. Present efforts are focused on the development of novel strategies, including chaperone-mediated enzyme enhancement and genetically engineered stem cell therapy. In the coming decades, a broadening therapeutic horizon for patients with inborn errors of metabolism is anticipated, and the growing experience in the management of patients with LSDs will serve as an instructive model. Among the many challenges will be determination of the extent to which these therapies have modified the course of disease beyond merely extending the age of survival, but also enabling a meaningful patient quality of life, and the minimisation of current resource use. The projected lifetime acquisition costs of newly introduced therapeutic options also raises several issues, related to equitable access and the large opportunity costs for other therapeutic areas, that will need to be addressed by healthcare policy makers and third-party payers.

Animals↗
PubMedDate not supplied

Biotech pharmaceuticals and biotherapy: an overview.

Broadly, the history of pharmaceutical biotechnology includes Alexander Fleming"s discovery of penicillin in a common mold, in 1928, and the subsequent development-prompted by World War II injuries-of large-scale manufacturing methods to grow the organism in tanks of broth. Pharmaceutical biotechnology has since changed enormously. Two breakthroughs of the late 1970s became the basis of the modern biotech industry: the interspecies transplantation of genetic material, and the fusion of tumor cells and certain leukocytes. The cells resulting from such fusion-hybridomas-replicate endlessly and can be geared to produce specific antibodies in bulk. Modern pharmaceutical biotechnology encompasses gene cloning and recombinant DNA technology. Gene cloning comprises isolating a DNA-molecule segment that corresponds to a single gene and synthesizing ("copying") the segment. Recombinant DNA technology, or gene splicing, comprises altering genetic material outside an organism-for example, by inserting into a DNA molecule a segment from a very different DNA molecule-and making the altered material (recombinant DNA) function in living things. Recombinant DNA technology enables modifying microorganisms, animals, and plants so that they yield medically useful substances, particularly scarce human proteins (by giving animals human genes, for example). This review, however, focuses not on pharmaceutical biotechnology"s methods but on its products, notably recombinant pharmaceuticals. It describes various types of biotech pharmaceuticals, their safety and effectiveness relative to the safety and effectiveness of conventionally produced pharmaceuticals, and the regulation of biotech pharmaceuticals.

Animals↗
PubMed2001

Dissecting the electrostatic interactions and pH-dependent activity of a family 11 glycosidase.

Previous studies of the low molecular mass family 11 xylanase from Bacillus circulans show that the ionization state of the nucleophile (Glu78, pK(a) 4.6) and the acid/base catalyst (Glu172, pK(a) 6.7) gives rise to its pH-dependent activity profile. Inspection of the crystal structure of BCX reveals that Glu78 and Glu172 are in very similar environments and are surrounded by several chemically equivalent and highly conserved active site residues. Hence, there are no obvious reasons why their apparent pK(a) values are different. To address this question, a mutagenic approach was implemented to determine what features establish the pK(a) values (measured directly by (13)C NMR and indirectly by pH-dependent activity profiles) of these two catalytic carboxylic acids. Analysis of several BCX variants indicates that the ionized form of Glu78 is preferentially stabilized over that of Glu172 in part by stronger hydrogen bonds contributed by two well-ordered residues, namely, Tyr69 and Gln127. In addition, theoretical pK(a) calculations show that Glu78 has a lower pK(a) value than Glu172 due to a smaller desolvation energy and more favorable background interactions with permanent partial charges and ionizable groups within the protein. The pK(a) value of Glu172 is in turn elevated due to electrostatic repulsion from the negatively charged glutamate at position 78. The results also indicate that all of the conserved active site residues act concertedly in establishing the pK(a) values of Glu78 and Glu172, with no particular residue being singly more important than any of the others. In general, residues that contribute positive charges and hydrogen bonds serve to lower the pK(a) values of Glu78 and Glu172. The degree to which a hydrogen bond lowers a pK(a) value is largely dependent on the length of the hydrogen bond (shorter bonds lower pK(a) values more) and the chemical nature of the donor (COOH > OH > CONH(2)). In contrast, neighboring carboxyl groups can either lower or raise the pK(a) values of the catalytic glutamic acids depending upon the electrostatic linkage of the ionization constants of the residues involved in the interaction. While the pH optimum of BCX can be shifted from -1.1 to +0.6 pH units by mutating neighboring residues within the active site, activity is usually compromised due to the loss of important ground and/or transition state interactions. These results suggest that the pH optima of an enzyme might be best engineered by making strategic amino acid substitutions, at positions outside of the "core" active site, that electrostatically influence catalytic residues without perturbing their immediate structural environment.

Amino Acid Sequence↗
PubMed2000

[Cloning and expression of a resistant Culex gene in Escherichia coli].

Recombinant plasmid pRLB1 was constructed from detoxifying gene B1 of pesticide resistant Culex pipiens quinquefasciatus and from plasmid pRL439 contained the strong promoter PpsbA. The positive clone was identified by digestion and Southern analysis. Expression of recombinant plasmid containing esterase gene was detected. An engineered bacterium possessing high enzyme activity was obtained and immobilized. It can effectively degrade the specific substrate alpha-naphthyl acetate (alpha-NA) and beta-naphthyl of esterase enzyme. Assays showed that pesticide acetofenate (7504 an organic choride pesticide) was degraded by the immobilized cells within one hour.

Animals↗
PubMed1992

Enhanced CO2/O2 specificity of a site-directed mutant of ribulose-bisphosphate carboxylase/oxygenase.

The CO2/O2 specificity factor of ribulose-bisphosphate carboxylase/oxygenase partially determines the efficiency of photosynthetic carbon assimilation. Heretofore, engineered alterations of the enzyme have only decreased the selectivity for CO2 utilization. We show that alanyl replacement of active-site Ser-368 of the Rhodospirillum rubrum carboxylase enhances the carboxylation selectivity approximately 1.6-fold over the wild-type level. This enhancement reflects a greater relative decline in oxygenase efficiency than in carboxylase efficiency. In contrast to wild-type enzyme, the carboxylase activity of the Ser-368 mutant protein is not perceptibly inhibited by O2, perhaps indicative of a change in rate-limiting steps in the overall reaction pathway.

Carbon Dioxide↗
PubMed1990

[Detection of aquatic microorganisms from the Black Sea--producers of restriction endonucleases].

300 clones of microorganisms isolated at different stations and from different depths in the Black Sea were screened for restriction endonucleases production. The production of restriction endonucleases was found in 17 clones screened. Three of them were identified to be Alteromonas haloplanktis B1. Restriction endonuclease AhaB1 is an isoshizomer of Sau961. An identified Alteromonas haloplanktis clone B8 produces AhaB8I restriction endonuclease the prototype to which is KpnI. Of the clones isolated three are Moraxella species B4 producing MapB4I restriction endonuclease analogous to BanI, three are Bacillus species producing BspB2I and one is Micrococcus lylae 113 producing Mly1131 analogue of NarI, six Moraxella species B6 produce MspB6I. The isolated producer strains may be used for isolation of above mentioned restriction endonucleases.

Bacteria↗
PubMed1987

[Development of rational methods for purifying restriction endonucleases].

The work deals with the search for rational schemes of the purification of endonucleases, suitable for the isolation of different enzymes. The scheme using the combination of Blue Sepharose and phosphocellulose has proved to be most universal. The expediency of starting the purification of Haemophilus enzymes on biogel A-0.5m has been established.

Bacteria↗
PubMed1988

Biotechnological treatment of industrial waste water.

The production of toxic or recalcitrant waste effluents by the chemical industry is leading to major problems of their disposal. New biotechnological approaches are now being used which will enable biological treatment of these wastes and will, in future, replace existing methods of effluent treatment.

Bacteria↗