Romany Abskharon - Academia.edu (original) (raw)

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Papers by Romany Abskharon

Reduction of toxic hexavalent was studied by using four resistant strains of E. coli ASU 3, 7, 8 ... more Reduction of toxic hexavalent was studied by using four resistant strains of E. coli ASU 3, 7, 8 and 18 isolated from wastewater of EL-Malah canal located in Assuit city, Egypt. They showed relatively high minimal inhibitory concentrations (MIC) and found to be plasmid mediated with 65 and 27 Kb. E. coli ASU 7 represents the best with high resistance and reducing power of Cr (VI), so it may be a suitable candidate for bioremediation. Alternation of protein profile in SDS-PAGE of the above strain was carried out under different concentrations of chromium stress.

Scientific reports, 2013

Prion diseases are associated with the conformational conversion of the cellular prion protein (P... more Prion diseases are associated with the conformational conversion of the cellular prion protein (PrP(C)) into the pathological scrapie isoform (PrP(Sc)) in the brain. Both the in vivo and in vitro conversion of PrP(C) into PrP(Sc) is significantly inhibited by differences in amino acid sequence between the two molecules. Using protein misfolding cyclic amplification (PMCA), we now report that the recombinant full-length human PrP (rHuPrP23-231) (that is unglycosylated and lacks the glycophosphatidylinositol anchor) is a strong inhibitor of human prion propagation. Furthermore, rHuPrP23-231 also inhibits mouse prion propagation in a scrapie-infected mouse cell line. Notably, it binds to PrP(Sc), but not PrP(C), suggesting that the inhibitory effect of recombinant PrP results from blocking the interaction of brain PrP(C) with PrP(Sc). Our findings suggest a new avenue for treating prion diseases, in which a patient's own unglycosylated and anchorless PrP is used to inhibit PrP(Sc) ...

$Research paper thumbnail of Crystallization and preliminary X-ray diffraction analysis of a specific VHH domain against mouse prion protein$

Acta crystallographica. Section F, Structural biology and crystallization communications, 2010

Prion disorders are infectious diseases that are characterized by the conversion of the cellular ... more Prion disorders are infectious diseases that are characterized by the conversion of the cellular prion protein PrPC into the pathogenic isoform PrPSc. Specific antibodies that interact with the cellular prion protein have been shown to inhibit this transition. Recombinant VHHs (variable domain of dromedary heavy-chain antibodies) or nanobodies are single-domain antibodies, making them the smallest antigen-binding fragments. A specific nanobody (Nb_PrP_01) was raised against mouse PrPC. A crystallization condition for this recombinant nanobody was identified using high-throughput screening. The crystals were optimized using streak-seeding and the hanging-drop method. The crystals belonged to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a=30.04, b=37.15, c=83.00 Å, and diffracted to 1.23 Å resolution using synchrotron radiation. The crystal structure of this specific nanobody against PrPC together with the known PrPC structure may help in understanding the PrP...

World Journal of Microbiology and Biotechnology, 2010

The current study describes the isolation and characterization of E. coli from wastewater that co... more The current study describes the isolation and characterization of E. coli from wastewater that collected from El-Malah canal in Assiut, Egypt. Twelve isolates were investigated for heavy metal resistance by which one of them showed multiple metal resistances. Furthermore, the bacterium was identified as E. coli ASU3 according to biochemical tests and then, preserved at Assuit University Mycological Centre with accession number AUMC B83. It exhibited high minimal inhibitory concentrations for metals and antibiotic resistance. The order of metals toxicity to the bacterium was Cr 6? [ Cu 2? [ Co 2? [ Pb 2? [ Ni 2? [ Cr 3? [ Cd 2? [ Zn 2? . Total protein content of E. coli ASU3 decreased with the increase of copper concentration.

World Journal of Microbiology and Biotechnology, 2009

The optimization of hexavalent chromium biosorption has been studied by using three different bio... more The optimization of hexavalent chromium biosorption has been studied by using three different biosorbents; biofilm of E. coli ASU 7 supported on granulated activated carbon (GAC), lyophilized cells of E. coli ASU 7 and granulated activated carbon. Supporting of bacteria on activated carbon decreased both the porosity and surface area of the GAC. Significant decrement of surface area was correlated to the blocking of microspores as a result of the various additional loads. The experimental data of adsorption was fitted towards the models postulated by Langmuir and Freundlich and their corresponding equations. The maximum biosorption capacity for hexavalent chromium using biofilm, GAC and E. coli ASU 7 were 97.70, 90.70, 64.36 mg metal/g at pH 2.0, respectively. Biosorption mechanism was related mainly to the ionic interaction and complex formation. Based on the experimental conditions, the presence of bacteria could be enhanced the capacity of activated carbon to adsorb hexavalent chromium ions from aqueous solutions.

Protein Engineering Design and Selection, 2011

Prion proteins (PrPs) are difficult to crystallize, probably due to their inherent flexibility. S... more Prion proteins (PrPs) are difficult to crystallize, probably due to their inherent flexibility. Several PrPs structures have been solved by nuclear magnetic resonance (NMR) techniques; however, only three structures were solved by X-ray crystallography. Here we combined in-situ proteolysis with automated microseed matrix screening (MMS) to crystallize two different PrP(C)-nanobody (Nb) complexes. Nanobodies are single-domain antibodies derived from heavy-chain-only antibodies of camelids. Initial crystallization screening conditions using in-situ proteolysis of mouse prion (23-230) in complex with a nanobody (Nb_PrP_01) gave thin needle aggregates, which were of poor diffraction quality. Next, we used these microcrystals as nucleants for automated MMS. Good-quality crystals were obtained from mouse PrP (89-230)/Nb_PrP_01, belonged to the monoclinic space group P 1 21 1, with unit-cell parameters a = 59.13, b = 63.80, c = 69.79 Å, β = 101.96° and diffracted to 2.1 Å resolution using synchrotron radiation. Human PrP (90-231)/Nb_PrP_01 crystals belonged to the monoclinic space group C2, with unit-cell parameters a = 131.86, b = 45.78, c = 45.09 Å, β = 96.23° and diffracted to 1.5 Å resolution. This combined strategy benefits from the power of the MMS technique without suffering from the drawbacks of the in-situ proteolysis. It proved to be a successful strategy to crystallize PrP-nanobodies complexes and could be exploited for the crystallization of other difficult antigen-antibody complexes.

Microbial Cell Factories, 2012

Expression of eukaryotic proteins in Escherichia coli is challenging, especially when they contai... more Expression of eukaryotic proteins in Escherichia coli is challenging, especially when they contain disulfide bonds. Since the discovery of the prion protein (PrP) and its role in transmissible spongiform encephalopathies, the need to obtain large quantities of the recombinant protein for research purposes has been essential. Currently, production of recombinant PrP is achieved by refolding protocols. Here, we show that the co-expression of two different PrP with the human Quiescin Sulfhydryl OXidase (QSOX), a human chaperone with thiol/disulfide oxidase activity, in the cytoplasm of E. coli produces soluble recombinant PrP. The structural integrity of the soluble PrP has been confirmed by nuclear magnetic resonance spectroscopy, demonstrating that properly folded PrP can be easily expressed in bacteria. Furthermore, the soluble recombinant PrP produced with this method can be used for functional and structural studies.

Journal of the American Chemical Society, 2014

Prions are fatal neurodegenerative transmissible agents causing several incurable illnesses in hu... more Prions are fatal neurodegenerative transmissible agents causing several incurable illnesses in humans and animals. Prion diseases are caused by the structural conversion of the cellular prion protein, PrP C , into its misfolded oligomeric form, known as prion or PrP Sc . The canonical human PrP C (HuPrP) fold features an unstructured N-terminal part (residues 23−124) and a well-defined C-terminal globular domain (residues 125−231). Compelling evidence indicates that an evolutionary N-terminal conserved motif AGAAAAGA (residues 113−120) plays an important role in the conversion to PrP Sc . The intrinsic flexibility of the N-terminal has hampered efforts to obtain detailed atomic information on the structural features of this palindromic region. In this study, we crystallized the full-length HuPrP in complex with a nanobody (Nb484) that inhibits prion propagation. In the complex, the prion protein is unstructured from residue 23 to 116. The palindromic motif adopts a stable and fully extended configuration to form a three-stranded antiparallel β-sheet with the β1 and β2 strands, demonstrating that the full-length HuPrP C can adopt a more elaborate β0-β1-α1-β2-α2-α3 structural organization than the canonical β1-α1-β2-α2-α3 prion-like fold. From this structure, it appears that the palindromic motif mediates β-enrichment in the PrP C monomer as one of the early events in the conversion of PrP C into PrP Sc .

Journal of Basic Microbiology, 2008

Sixty six isolates of Pseudomonas spp. were isolated from wastewater of El-Malah canal located in... more Sixty six isolates of Pseudomonas spp. were isolated from wastewater of El-Malah canal located in Assiut, Egypt and were checked for their heavy metal tolerance. One isolate has tested for its multiple metal resistances and found to be plasmid mediated with molecular weight 27 Kb for nickel and lead. It was identified as Pseudomonas aeruginosa ASU 6a. Its minimal inhibitory concentration (MIC) for Cu 2+ , Co 2+ , Ni 2+ , Zn 2+ , Cr 3+ , Cd 2+ and Pb 2+ were 6. 3, 5.9, 6.8, 9.2, 5.8, 4.4, and 3.1 mM, respectively. Growth kinetics and the maximum adsorption capacities were determined under Ni 2+ and Pb 2+ stress. The latter heavy metals induced potassium efflux and were used as indicator for plasma membrane permeabilization.