The experiments described in this thesis involve the expression and characterisation of recombinant truncated thioredoxin (tTrx) and the potential involvement that thioredoxin (Trx) has in the cellular responses to oxidative stress. Truncated Trx (80 amino acids) was expressed from a plasmid containing the ORF for tTrx that had been introduced into E.coli BL-21(DE3) cells. The protein was initially extracted using a combination of high concentrations of urea, high pH levels, and multiple sonification steps to remove the tTrx from inclusion bodies formed during expression. This procedure produced a stable solution of tTrx. Purification of tTrx from this protein solution required anion exchange chromatography followed by gel permeation in a HPLC system to obtain fully purified, recombinant tTrx which allowed further characterisation studies to be undertaken. An initial investigation into tTrx was performed to determine some basic physical, biochemical and functional aspects of this hitherto relatively undefined protein. Analysis by sedimentation equilibrium indicated that freshly prepared tTrx forms a single species with a molecular weight of 18.8kDa. This value indicates that recombinant tTrx naturally forms a dimer in solution that was shown to be non-covalent in nature and stable in solution. The capacity of tTrx to reduce protein disulphide bonds was determined using the insulin reduction assay. Results show that tTrx lacks this particular redox ability. The rate of oxidisation at 4 degrees C was analysed using free thiol determination, sedimentation equilibrium and SDS-PAGE patterning. Results indicated a steady rise in the degree of oxidation of tTrx over an eight day period. After six days the oxidated protein consistently displayed the presence of intramolecular disulphide bonds. Covalently-linked disulphide dimers and higher molecular weight oligomers were detectable after eight days oxidation. An investigation of the reducing capacity of the basic Trx system determined that fully oxidised tTrx was unable to act alone as a substrate for thioredoxin reductase (TR). However, when reduced Trx was added to the system, it appeared capable of acting as an electron donor to the oxidised tTrx in order to reduce disulphide groups. Recombinant tTrx was successfully radiolabelled with Trans 35S-methionine/cysteine for use in cell association studies. No evidence was found to indicate the presence of a receptor for tTrx on either MCF-7 or U-937 cells. Findings suggest that a low level of non-specific binding of tTrx to these cell lines rather than a classical ligand-binding mechanism occurs thus suggesting the absence of a cell surface receptor for tTrx. The role that Trx may play in the cellular responses to oxidative stress was also investigated. The chemical oxidants hydrogen peroxide (H2O2) and diamide were used to establish an in vitro model of oxidative stress for the choriocarcinoma cytotrophoblast cell line JEG-3. Cellular function was assessed in terms of membrane integrity, metabolic activity and the ability to synthesis new DNA following exposure to these oxidants. Results indicated that both agents were capable of causing cells to undergo oxidative stress without inducing immediate apoptosis or necrosis. Initially, JEG-3 cells exposed to 38μM or 75μM H2O2 or 100μM diamide were shown to display altered cell metabolism and DNA synthesis without loss to cell viability or membrane integrity. Cells were also shown to be capable of some short-term recovery but later lapsed into a more stressed state. Expression levels of Trx were studied to determine whether this type of chemical stress caused a change in intercellular protein levels. Both cELISA and western blotting results indicated that only cells exposed to 100μM diamide displayed any significant increase in Trx protein levels after 6 or 8hrs exposure to the oxidant. Further studies over a longer time-frame were also performed. These found that when JEG-3 cells were exposed to 18μM H2O2 or 200μM diamide over 12-48hrs, a positive correlation between increasing endogenous Trx protein levels and a decline in cell proliferation was observed. Cytotrophoblast cells, which are responsible for implantation and placentation, are susceptible to oxidative stress in vivo and their anti-oxidant capacity is fundamental to the establishment of pregnancy. The findings obtained during these studies suggest that Trx plays a role in this process.

Addenda held in pocket pasted onto back end paper. / Bibliography: leaves 137-165. / xvi, 165 leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis involves the retrospective investigation of the insulin-like growth factors and their binding proteins in the serum of children with chronic renal failure (CRF) and transplantation, before and after treatment with recombinant human growth hormone (rhGH). IGF-IGFBP complexes in pooled serum from prepubertal and pubertal children of both sexes with CRF and renal transplantation, before and after treatment with rhGH, are analysed by fast protein liquid chromatography under neutral conditions. / Thesis (M.D.)--University of Adelaide, Dept. of Paediatrics, 1997?

<p>This thesis examines the Swedish political response to the challenges posed by gene technology, seen through the prism of governmental commissions. It discerns and analyses continuities and changes in the Swedish political conception of gene technology, over the course of two decades, 1980–2000. This is done by thematically following ideas of “risks” and “ethics” as they are represented in the inner workings and reception of three governmental commissions. The Gene-Ethics Commission (1981–1984), the Gene Technology Commission (1990–1992) and the Biotechnology Commission (1997–2000) form the empirical focal points of this analysis. The first two provided preparatory policy proposals that preceded the implementation of the Swedish gene technology laws of 1991 and 1994. The last one aimed at presenting a comprehensive Swedish biotechnology policy for the new millennium.</p><p> The study takes into account the role of governmental commissions as arenas where science and politics intersect in Swedish political life, and illuminates how this type of “boundary organisation”, placed on the border of science and politics, impinges on the understanding of the gene technology issue. The commissions have looked into the limits, dangers, possibilities and future applications of gene technology. They have been appointed to deal with the problematic task of distinguishing between what is routine and untested practices, realistic prediction and “science fiction”, what are unique problems and what are problems substantially similar to older ones, what constitutes a responsible approach as opposed to misconduct and what it means to let things “get out of hand” in contrast to being “in control”. Throughout a period of twenty years, media reports have continued to frame the challenges posed by gene technology as a task of balancing risks and benefits, walking the fine line between “frankenfoods” and “miracle drugs”. </p><p>One salient problem for the commissions to solve was that science and industry seemed to promote a technology the public opposed and resisted, at least in parts. For both politics and science to gain, or regain, public trust it needed to demonstrate that risks – be it environmental, ethical or health related ones – were under control. Under the surface, it was much more complicated than “science helping politics” to make informed and rational decisions on how to formulate a regulatory policy. Could experts be trusted to participate in policy-making in a neutral way and was it not important, in accordance with democratic norms, to involve the public? </p>

<p>Sarcoptes scabiei is a disease-causing parasitic mite of humans and animals that is prevalent worldwide. The parasite lives in burrows in the epidermis of its host. These burrows are formed by a combination of mechanical destruction by the mite and secretion of various factors.</p><p>The enzyme superoxide dismutase (SOD) catalyzes the dismutation of superoxide into oxygen and hydrogen peroxide. As such, it is an important antioxidant defense in nearly all cells exposed to oxygen. In this project, the enzyme was expressed in transformed Escherichia coli cells. The SOD cDNA from S. scabiei was ligated into two different expression vectors: pPU16 and pET-14b. The S. scabiei SOD open reading frame reported here is 696 nucleotides long and yields a protein with a molecular weight of  69.5 kDa. Only one of the constructs was successfully created, using pPU16. The construct was designated pPU110 and has a sequence coding for a hexahistidine tag downstream of the SOD cDNA and has a sequence coding for the maltose binding protein (MBP) upstream.</p><p>The expression plasmid pPU110 was verified by DNA-sequencing and the tested in different expression experiments. Analysis using SDS-PAGE showed that recombinant fusion SOD could be readily expressed in E.coli.</p>

Thesis (Ph.D.)--Baylor University, 2005. / Includes bibliographical references (p. 145-157).

Organophosphate hydrolase (OPH, EC 3.1.8.1) is a bacterial enzyme with a broad spectrum of potential substrates that include organophosphorus pesticides, herbicides, and chemical warfare agents. OPH has been expressed successfully in bacterial, fungal, and insect cell culture systems; however, none of these systems produces amounts of enzyme suitable for applications outside of the research laboratory. Therefore, a transgenic Zea mays L. (maize) system was developed to express OPH as an alternate to the current OPH expression systems. The bacterial gene encoding the OPH protein was optimized for transcriptional and translational expression in maize. The optimized gene was inserted into the maize genome under the control of embryo specific, endosperm specific, and constitutive plant promoters. Select transformants were analyzed for the expression of OPH. Expression was observed in the seeds of plants transformed with each of the three constructs with the highest expression observed with the embryo specific and constitutive promoter constructs. The highest OPH expressing lines of transgenic maize had expression levels higher than those reported for the E. coli expression system. OPH was purified from transgenic maize seed and analyzed for posttranslational modification and kinetic properties. OPH was observed to undergo a glycosylation event when expressed in maize that yielded at least two forms of OPH homogolous dimer. The glycosylated form of OPH bound tightly to the Concanavalin A sepharose and remained active after months of storage at room temperature. OPH activity was checked against a number of organophosphate herbicides. Enzymatic activity was observed against the herbicide Amiprophos-methyl and kinetic properties were measured. Enzymatic activity was also tested against the organophosphate Haloxon. Transgenic maize callus, leaf, and seed tissue could be screened for the presence of the optimized opd gene by enzymatic activity. Comparison of the growth of transgenic and control callus on media containing organophosphates showed that the transgenic callus was resistant to the herbicidal effects of haloxon. Transgenic plants expressing OPH were also resistant to the herbicide bensulide when compared to control plants. This indicates that OPH can be used as a screenable marker in plant systems and may be a potential scorable marker system as well.

The goal of this work was to contribute to the fed-batch process optimisation task by deriving parameters that have considerable impact on productivity as well as product quality The chosen parameters were I) the design of the glucose feed profile, II) the choice of induction strategy, with respect to the method of addition, and III) the time of the induction, with respect to the specific glucose consumption rate. The present fed-batch experiments using the lacUV5-promoter, for production of b-galactosidase, have shown that a high glucose feed rate gives a specific production rate, qp, that is twice as high, after induction, compared to a feed rate that is 2.5 times lower. The constant accumulation of lacZ-mRNA indicates that the translational capacity is initially limiting the synthesis machinery, but after four hours of maximum specific production and a corresponding drop in lacZ-mRNA production, the cultivation is likely to be transcription limited. The high feed-rate system resulted in high accumulation of β-galactosidase, corresponding to 40% of total cellular proteins. By design of feed profiles in a fed-batch process the detrimental effects of overflow metabolism, giving acetic acid formation, can be avoided. However, the results show that a one-dose addition of isopropyl-β-D-galactopyranoside (IPTG), provokes a non-growth associated production of acetic acid. This response can be alleviated by; lowering the inducer concentration (in this case to below 165 μM), by further reducing the feed rate of glucose or by using alternative induction methods. The use of a stepwise addition or a feed of IPTG thus delayed and reduced the level of acetic acid accumulation. It was also shown that a small change in the time-point of induction lead to large variability, regarding both productivity and acetic acid accumulation, in a fed-batch cultivation, In order to further investigate the protein quality two additional proteins were studied in fed-batch cultivations using high and low glucose feed. The aim was to prove the hypothesis that the feed related change in the rate of synthesis of the nascent polypeptide controls the product quality. For the two proteins: Zb-MalE (wt) and Zb-MalE31 (mutant), the transcription rate, in terms of amount of IPTG, and translation rate, in terms of changes in feed rate, influences the percentage of inclusion body formation and degradation of nascent polypeptide. The data show a higher rate of inclusion body formation for the model protein Zb-MalE31 during high feed rate cultivations, as well as at high levels of inducer. Furthermore, the rate of proteolysis was significantly higher for a high feed rate. The high feed rate thus results in a higher rate of synthesis but a lower corresponding quality, for the model proteins studied. In the present investigation of fed-batch cultivations using several different expression vectors, it was found that the central alarmone guanosine tetraphosphate (ppGpp) was formed at both high and low feed rates upon induction. It could be shown, however, that by secretion of Zb-MalE to the periplasm, the stringent response could be avoided. This might be due to the decreased burden on the host where the secretion of product further seems to make the cell able to redirect the carbon flux from overflow metabolism, since no acetic acid was produced. The secretion also demonstrates that the growth arrest could be aborted, which is otherwise gained in the PmalK production system. A novel fed-batch process based on the promoters for the universal stress proteins A and B (PuspA, PuspB) was designed to make use of these powerful promoters in an industrial production context. It was concluded that the process had to start from a high specific growth rate and induction was performed once a limiting feed started. This was done to purposely induce the stringent response and/or acetic acid accumulation since this was required for induction. In the suggested system, induction has to be performed and maintained at continuous substrate feeding, whilst avoiding exceeding the cellular capacity, since the stationary phase starvation alone did not lead to production. In conclusion, a new stress induction based production system was achieved resulting in high accumulations of product protein without any detected metabolic side effects. / <p>QC 20101008</p>

Helicobacter pylori infects and persistently colonizes the stomach, which results in gastritis and in some individuals peptic ulcer disease or gastric cancer. Adherence of H. pylori to the epithelium is an important factor for development of disease. Attachment is mediated by the adhesins BabA and SabA that binds the ABO/Leb blood group antigens and sialylated glycoconjugates respectively.  High-affinity attachment could be anticipated to be of disadvantage for H. pylori because epithelial cells have a fast turnover rate and the dislocated and shed epithelial cells would carry attached bacteria to the acidic gastric juice in the lumen. However, here we describe that H. pylori manage to adapt to this innate clearance mechanism by unique acid regulatory binding properties of its adhesins. We propose that pH regulated binding properties enable bacteria to detachment from host cells for chemotactic guided motility and successful return to the more neutral epithelium for a fresh restart of the infectious cycle. By comparison of BabA from different stomach loci we identified amino acid key position for acid regulated binding activity. Previous studies found lower prevalence of Leb-binding among H. pylori isolates from southern Europe compared to Sweden. Here we tested if the reduced prevalence of Leb-binding could be explained by a novel binding mode; in among Spanish strains, we identified S812 that demonstrates preference for multivalent binding to ABO antigens in glycolipids; we found that 812 BabA had drifted in its preferred binding epitope away from the consensus a1,2fucosylation and towards the blood group A and B derivatives. Such epitope drift might in particular optimize binding to ABO antigens in densely packed lipid rafts. In parallel, we studied the influence of BabA for disease progression by an inventory of gastric biopsies. BabA correlated both with the oncoprotein CagA, the VacAs1 toxin and, in addition, to severe disease progression. We further correlate BabA expression with positive secretor phenotype and stronger adhesion of H. pylori in vitro. For functional adherence studies in vitro, we constructed a recombinant Leb-expressing cell lineage that supports BabA mediated H. pylori attachment.

Transglutaminases (EC 2.3.2.13) are enzymes that catalyze an acyl transfer reaction between a &gamma / -carboxyamide group of a peptide bound glutaminyl residue (acyl donor) and a variety of primary amines (acyl acceptors), including the amino group lysine. Transglutaminase has a potential in obtaining proteins with novel properties, improving nutritional quality of foods with the addition of essential amino acids, preparing heat stable gels, developing rheological properties and mechanical strength of foods and reducing the applications of food additives. The aim of this study is to develop intracellular and extracellular microbial protransglutaminase (pro-MTG) producing recombinant Pichia pastoris strains by using genetic engineering techniques. In this context first,protransglutaminase gene (pro-mtg) from Streptomyces mobaraensis was amplified by PCR both for intracellular and extracellular constructs using proper primers then they were cloned into the pPICZ&alpha / -A expression vectors, separately. Both intracellular (pPICZ&alpha / A::pro-mtgintra) and extracellular (pPICZ&alpha / A::pro-mtgextra) constructs were prepared with strong alcohol oxidase 1 promoter which is induced by methanol. Pichia pastoris X33 cells were transfected by linear pPICZ&alpha / A::pro-mtgintra and pPICZ&alpha / A::pro-mtgextra, separately and plasmids were integrated into the Pichia pastoris X33 genome at AOX1 locus. After constructing the recombinant P. pastoris strains, batch shaker bioreactor experiments were performed for each recombinant cell and the best producing strains were selected according to Dot blot and SDS-PAGE analyses. The selected recombinant P. pastoris strains, carrying pPICZ&alpha / A::promtgextra gene and pPICZ&alpha / A::pro-mtgintra gene in their genome were named as E8 and I1, respectively. Afterwards, a controlled pilot scale bioreactor experiment in a working volume of 1 L was performed with E8 clone and produced pro-MTG was activated by Dispase I. The variations in the recombinant MTG activity, cell concentration, total protease activity, AOX activity and organic acid concentrations throughout the bioprocess were analyzed and specific growth rates, specific consumption rates and yield coefficients were calculated regarding to measured data. Maximum MTG activity was obtained as 4448 U L- 1 and the maximum cell concentration was measured as 74.1 g L-1 at t=36 h of the bioprocess. In this study, an active transglutaminase enzyme was produced extracellularly by P. pastoris for the first time and the third highest extracellular MTG activity was achieved with E8 clone.

Ribonucleotide reductase is a remarkable enzyme that catalyzes the rate-limiting step in the synthesis of the 2'-deoxynucleoside triphosphates. The intent of this project was to characterize the ribonucleotide reductase encoded by the orthopoxvirus, vaccinia. The first objective was to study the structural and functional features of the viral small subunit protein of ribonucleotide reductase. The viral reductase gene was engineered into an expression vector and expressed in Escherichia coli. The purified recombinant protein was then characterized and compared with other ribonucleotide reductase small subunits from different organisms. The physical characteristics of the vaccinia virus enzyme showed a strong similarity to the features of the mammalian counterpart. A second aim of this project was to establish the transcriptional and translational kinetics of ribonucleotide reductase gene expression during the time course of viral infection in cultured mammalian cells. In addition, the activity and stability of the enzyme in the viral system was measured and the accumulation of ribonucleotide reductase protein was quantitated. By also quantitating the accumulation of viral DNA synthesis, a direct comparison can be made between the the synthesis and utilization of deoxynucleotide precursors. A third objective of this work was to detail the mechanism by which hydroxyurea inactivates the vaccinia virus ribonucleotide reductase. Visible spectroscopy and electron paramagnetic resonance spectroscopy clearly demonstrated that the inhibitor destroys the free radical moiety in the viral small subunit protein. In addition, in vivo studies revealed that inhibition by hydroxyurea can be circumvented during viral infection. The exogenous addition of deoxyadenosine reversed the block to viral growth that was imposed by hydroxyurea, and stabilized hydroxyurea induced deoxynucleotide pool imbalances. These inhibition studies suggest that there may be a differential sensitivity of the enzyme towards hydroxyurea in the presence of various substrates. / Graduation date: 1993