Expression optimisation of recombinant α-Larabinofuranosidase from Aspergillus niger ATCC 120120 in Pichia pastoris and its biochemical characterisation

A gene encoding α-L-arabinofuranosidase (AnabfA) from Aspergillus niger ATCC 120120 was successfully cloned and expressed in Pichia pastoris under the control of the AOX1 promoter. The effect of cultural conditions on recombinant AnabfA production was studied and the enzyme was expressed as a soluble protein. Recombinant AnabfA was expressed as an active enzyme at 28°C when cultured in BMMY medium (pH 6.0) and induced with 2% methanol every 24 h. Maximum activity was observed 5 days after induction. The purified recombinant AnabfA before and after treatment with PNGase F migrated by SDS-PAGE had relative molecular masses of about 83 and 66 kDa, respectively, suggesting that the AnabfA contains N-linked oligosaccharides. Characterisation of the purified recombinant AnabfA showed an optimum temperature and pH of 50°C and 4, respectively. The enzyme was stable at a pH of 3 to 6 and retained more than 80% of its activity after pre-incubation at 40°C for 30 min. The recombinant AnabfA activity was stimulated by K+, Mn2+, Na2+ and triton X-100 and was strongly inhibited by Cu2+ and Fe2+ and the enzyme activity was relatively unaffected by Ca2+, CO2+, Mg2+ and EDTA. The Km and Vmax of the purified recombinant AnabfA activity towards ρNPA were 0.93 mM and 17.86 μmol/ml/min, respectively.Key words: Aspergillus niger, α-L-arabinofuranosidase, expression, Pichia pastoris, characterisation

Effect of demographic variables on public attitudes towards genetically modified insulin

Earlier studies on public attitude and risk perception have concluded that the public’s attitudes towards biotechnology was primarily driven by several factors such as familiarity, perceived benefits, perceived risks, risk acceptance, moral concerns and encouragement. Demographic characteristics have been known to affect attitudes towards science. The purpose of this paper is to compare the attitude of the Malaysian public towards genetically modified (GM) insulin across several background variables such as religion, race, education level and age. A survey was carried out on 1017 respondents stratified according to various stakeholder groups in the Klang Valley region. Analyses of Variance (ANOVAs) showed significant differences in the mean scores for familiarity of GM insulin across religions, races and ages but not across education levels and gender. Both perceived benefits and perceived risks were found to differ across races, education levels and gender but not across religions and ages. On the other hand, moral concern was found to differ in all four background variables except gender while risk acceptance differed across races and gender and encouragement only differed across education  levels. In conclusion, background variables do have a significant effect on some of the dimensions of Malaysians’ attitudes towards modern biotechnology. The research findings will be useful for understanding the effect of background variables on public attitudes towards the application of gene technology in medicine. More in-depth empirical studies should be carried out to understand the underlying causes behind the differences.Key words: Attitude, gene technology, medicine, GM (genetically modified) insulin, background variables, Malaysia

Overexpression, purification and characterization of the Aspergillus niger endoglucanase, EglA, in Pichia pastoris>/i>

Cellulases are industrially important hydrolytic enzymes applicable in the bioconversion of cellulosic biomass to simple sugars. In this work, an endoglucanase from Aspergillus niger ATCC 10574, EglA, was expressed in the methylotrophic yeast Pichia pastoris and the properties of the recombinant protein were characterized. The full length cDNA of eglA has been cloned into a pPICZαC expression vector and expressed extracellularly as a ~30 kDa recombinant protein in P. pastoris X-33. Pure EglA displayed optimum activity at 50°C and was stable between 30 and 55°C. The pH stability of this enzyme was shown to be in the range of pH 2.0 to 7.0 and optimum at pH 4.0. EglA showed the highest affinity toward β-glucan followed by carboxymethyl cellulose (CMC) with a specific activity of 63.83 and 9.47 U/mg, respectively. Very low or no detectable hydrolysis of cellobiose, laminarin, filter paper and avicel were observed. Metal ions such as Mn2+, Co2+, Zn2+, Mg2+, Ba2+, Fe2+, Ca2+ and K+ showed significant augmentation of endoglucanase activity, with manganese ions causing the highest increase in activity to about 2.7 fold when compared with the control assay, whereas Pd2+, Cu2+, SDS and EDTA showed inhibition of EglA activity.Key words: Cellulase, endoglucanase, recombinant, Aspergillus niger, Pichia pastoris

A Burkholderia pseudomallei Toxin Inhibits Helicase Activity of Translation Factor eIF4A

This is the author accepted manuscript. The final version is available from American Association for the Advancement of Science via the DOI in this record.The structure of BPSL1549, a protein of unknown function from Burkholderia pseudomallei, reveals a similarity to Escherichia coli cytotoxic necrotizing factor 1. We found that BPSL1549 acted as a potent cytotoxin against eukaryotic cells and was lethal when administered to mice. Expression levels of bpsl1549 correlate with conditions expected to promote or suppress pathogenicity. BPSL1549 promotes deamidation of glutamine-339 of the translation initiation factor eIF4A, abolishing its helicase activity and inhibiting translation. We propose to name BPSL1549 Burkholderia lethal factor 1

Fluorescence and evaporative light scattering HPLC profiling of intracellular asparagine (N)-linked oligosaccharides from Saccharomyces cerevisiae using the alg8 mutant

N-glycans are biologically important oligosaccharides associated with the asparagine residue that may exist in protein-bound or unbound forms in all eukaryotes (including yeasts) and some bacteria. The- core structure of these oligosaccharides is based on the trimannosyl chitobiose structure resulting from cellular N-glycosylation. Preparative-scale amounts of these oligosaccharides are important for chemical, structural and functional studies due to their biological significance. Therefore, we explored a biochemical approach of oligosaccharide preparation using mutant-derived monoglucosylated lipid-linked oligosaccharides (LLOs) required for the assembly of N-linked glycoproteins and non-monoglucosylated free-oligosaccharides (fOSs) from misfolded N-linked glycoproteins using an N-glycosylation (alg) mutant of Saccharomyces cerevisiae. Oligosaccharide extracts of fOSs and LLOs from the alg8 S. cerevisiae mutant lacking the ALG8 gene were profiled using fluorescence- and evaporative light scattering-based HPLC. LLOs did not produce accumulated levels of the target mutant- related monoglucosylated (Glc1Man9GlcNAc2) at 100 ml scale. However, it was possible to detect truncated oligomannose (paucimannose) structures in the fOSs of the alg8 mutant

Fluorescence and evaporative light scattering HPLC profiling of intracellular asparagine (N)-linked oligosaccharides from Saccharomyces cerevisiae using the alg8 mutant

N-glycans are biologically important oligosaccharides associated with the asparagine residue that may exist in protein-bound or unbound forms in all eukaryotes (including yeasts) and some bacteria. The- core structure of these oligosaccharides is based on the trimannosyl chitobiose structure resulting from cellular N-glycosylation. Preparative-scale amounts of these oligosaccharides are important for chemical, structural and functional studies due to their biological significance. Therefore, we explored a biochemical approach of oligosaccharide preparation using mutant-derived monoglucosylated lipid-linked oligosaccharides (LLOs) required for the assembly of N-linked glycoproteins and non-monoglucosylated free-oligosaccharides (fOSs) from misfolded N-linked glycoproteins using an N-glycosylation (alg) mutant of Saccharomyces cerevisiae. Oligosaccharide extracts of fOSs and LLOs from the alg8 S. cerevisiae mutant lacking the ALG8 gene were profiled using fluorescence- and evaporative light scattering-based HPLC. LLOs did not produce accumulated levels of the target mutant- related monoglucosylated (Glc1Man9GlcNAc2) at 100 ml scale. However, it was possible to detect truncated oligomannose (paucimannose) structures in the fOSs of the alg8 mutant