Figen Caliskan - Academia.edu (original) (raw)

Papers by Figen Caliskan

Turkish Journal of Biochemistry, 2009

Objectives: Despite the long history on proteolytic activity studies, no study has been reported ... more Objectives: Despite the long history on proteolytic activity studies, no study has been reported about the presence of proteases from the Turkish scorpion A. crassicauda venom which is among the most toxic species in the world. The present work is a preliminary study indicating the presence of gelatinolytic proteases in the A. crassicauda crude venom which almost nothing is known about its components.

GigaScience, May 18, 2022

Journal of Venomous Animals and Toxins including Tropical Diseases

Background: Scorpion neurotoxins such as those that modify the mammalian voltagegated sodium ion ... more Background: Scorpion neurotoxins such as those that modify the mammalian voltagegated sodium ion channels (Nav) are the main responsible for scorpion envenomation. Their neutralization is crucial in the production of antivenoms against scorpion stings. Methods: In the present study, two in silico designed genes-one that codes for a native neurotoxin from the venom of the Anatolian scorpion Androctonus crassicauda, named Acra 4-and another non-native toxin-named consensus scorpion toxin (SccTx) obtained from the alignment of the primary structures of the most toxic neurotoxins from the Middle Eastern and North African scorpions-were recombinantly expressed in E. coli Origami. Results: Following bacterial expression, the two expressed neurotoxins, hereafter named HisrAcra4 and HisrSccTx, were obtained from inclusion bodies. Both recombinant neurotoxins were obtained in multiple Cys-Cys isoforms. After refolding, the active protein fractions were identified with molecular masses of 8,947.6 and 9,989.1 Da for HisrAcra4 and HisrSccTx, respectively, which agreed with their expected theoretical masses. HisrAcra4 and HisrSccTx were used as antigens to immunize two groups of rabbits, to produce either anti-HisrAcra4 or anti-HisrSccTx serum antibodies, which in turn could recognize and neutralize neurotoxins from venoms of scorpion species from the Middle East and North Africa. The antibodies obtained from rabbits neutralized the 3LD 50 of Androctonus australis, Leiurus quinquestriatus hebraeus and Buthus occitanus venoms, but they did not neutralize A. crassicauda and A. mauritanicus venoms. In addition, the anti-HisrAcra4 antibodies did not neutralize any of the five scorpion venoms tested. However, an antibody blend of anti-HisrAcra4 and anti-HisrSccTx was able to neutralize A. crassicauda and A. mauritanicus venoms. Conclusions: Two recombinant Nav neurotoxins, from different peptide families, were used as antigens to generate IgGs for neutralizing scorpion venoms of species from the Middle East and North Africa.

Toxin synergism is a complex biochemical phenomenon, where different animal venom proteins intera... more Toxin synergism is a complex biochemical phenomenon, where different animal venom proteins interact either directly or indirectly to potentiate toxicity to a level that is above the sum of the toxicities of the individual toxins. This provides the animals possessing venoms with synergistically enhanced toxicity with a metabolic advantage, since less venom is needed to inflict potent toxic effects in prey and predators. Among the toxins that are known for interacting synergistically are cytotoxins from snake venoms, phospholipases A2 from snake and bee venoms, and melittin from bee venom. These toxins may derive a synergistically enhanced toxicity via formation of toxin complexes by hetero-oligomerization. Using a human keratinocyte assay mimicking human epidermis in vitro, we demonstrate and quantify the level of synergistically enhanced toxicity for 12 cytotoxin/melittin-PLA2 combinations using toxins from elapids, vipers, and bees. Moreover, by utilizing an interaction-based assay...

Phytotherapy Research, 1997

RESUMO: "Triagem antimicrobiana de algumas plantas medicinais do Cerrado de Mato Grosso". Os extr... more RESUMO: "Triagem antimicrobiana de algumas plantas medicinais do Cerrado de Mato Grosso". Os extratos em hexano, diclorometano, acetato de etila e etanol das entrecascas de Bowdichia virgilioides, Calophyllum brasiliense, Cariniana rubra, Lafoensia pacari e Stryphnodendron obovatum, do rizoma de Simaba ferruginea e do látex de Croton urucurana foram triados contra um painel de bactérias e fungos usando o método de microdiluição em caldo. O látex de Croton urucurana foi o material derivado de planta com maior atividade antimicrobiana. Os extratos em acetato de etila e hexano da entrecasca de Calophyllum brasiliense destacaram-se por suas seletivas atividades antibacterianas. Os extratos polares da entrecasca de Lafoensia pacari notabilizaram-se por suas potentes e seletivas atividades contra leveduras e os extratos polares e não-polares de Bowdichia virgilioides por suas atividades antifúngicas contra hialo-hifomicetos e dermatófitos. Este é o primeiro relato mostrando atividades antifúngicas para os extratos de Cariniana rubra e Simaba ferruginea. Esse trabalho demonstrou a atividade antimicrobiana de plantas medicinais do Cerrado de Mato Grosso em ensaios in vitro e indica que elas podem ser potenciais candidatas para o desenvolvimento de novas estratégias no tratamento de infecções bacterianas e fúngicas. Unitermos: Plantas medicinais, Cerrado de Mato Grosso, triagem antimicrobiana, ensaio de microdiluição em caldo.

Biomedicines, 2020

Scorpion venom may cause severe medical complications and untimely death if injected into the hum... more Scorpion venom may cause severe medical complications and untimely death if injected into the human body. Neurotoxins are the main components of scorpion venom that are known to be responsible for the pathological manifestations of envenoming. Besides neurotoxins, a wide range of other bioactive molecules can be found in scorpion venoms. Advances in separation, characterization, and biotechnological approaches have enabled not only the development of more effective treatments against scorpion envenomings, but have also led to the discovery of several scorpion venom peptides with interesting therapeutic properties. Thus, scorpion venom may not only be a medical threat to human health, but could prove to be a valuable source of bioactive molecules that may serve as leads for the development of new therapies against current and emerging diseases. This review presents both the detrimental and beneficial properties of scorpion venom toxins and discusses the newest advances within the dev...

Bu calismanin amaci; etanolun ve etanol ile aspirinin birlikte verilmesinin eritrosit membraninda... more Bu calismanin amaci; etanolun ve etanol ile aspirinin birlikte verilmesinin eritrosit membranindaki in vitro etkilerini aciklamaktir. Bununla birlikte s-adenozilmetiyonin’in (SAMe) muhtemel koruyucu etkisini degerlendirdik ve bu amac icin membrana bagli Na+-K+ ATPaz’in aktivitesini ve plazma malondialdehit (MDA), sialik asit (SA), duzeylerini tespit ettik. Konsantrasyon oranlari, etanol ( %0.5), aspirin (4 mg/ml) ve SAMe (2.5 nM) olarak ayarlanan kan ornekleri [etanol+aspirin+SAMe], [etanol+SAMe], [etanol+aspirin], etanol ve kontrol grubu olmak uzere 5 gruba ayrildi ve bu kan ornekleri 16 saat boyunca 25°C’de inkubasyona birakildi. Daha sonra bu numunelerde Na+ -K+ ATPaz, MDA, Sialik Asit duzeyleri calisildi. Etanol ve [etanol+SAMe] grubunun Na+ -K+ ATPaz aktiviteleri kontrol grubu ile mukayese edildiginde azaldigi goruldu (p<0.05). [Etanol+aspirin] ve [etanol+aspirin+SAMe] gruplarinda plazma MDA duzeyleri kontrol grubundan (p<0.001), [Etanol+aspirin] grubu da etanol grubundan...

GigaScience, 2021

Venom research is a highly multidisciplinary field that involves multiple subfields of biology, i... more Venom research is a highly multidisciplinary field that involves multiple subfields of biology, informatics, pharmacology, medicine, and other areas. These different research facets are often technologically challenging and pursued by different teams lacking connection with each other. This lack of coordination hampers the full development of venom investigation and applications. The COST Action CA19144–European Venom Network was recently launched to promote synergistic interactions among different stakeholders and foster venom research at the European level.

Toxicon, 2006

The soluble venom from the scorpion Androctonus crassicauda was fractionated by high performance ... more The soluble venom from the scorpion Androctonus crassicauda was fractionated by high performance liquid chromatography. At least 44 different sub-fractions were resolved and collected for finger print mass analysis using an electrospray mass spectrometer. This analysis revealed the presence of 80 distinct molecular mass components, from which five were further characterized. A peptide, named Acra1 was fully sequenced. It contains 58 amino acid residues crossbridged by six cysteines forming three disulfide pairs, with a molecular mass of 6497 Da. A second purified peptide named Acra2 was partially sequenced with a molecular mass of 7849 Da. Acra1 is toxic and Acra2 is lethal to mice, at the dose assayed. Additionally, a cDNA library of the venomous gland of one specimen was prepared and several clones were obtained among which is one that codes for Acra1. Three analog gene sequences were found with point mutations either in the section that corresponds to the mature peptide or to the signal peptide. The signal peptide is 22 amino acid residues long. Several other gene sequences obtained suggest the presence in this venom of three distinct groups of peptides, among which are peptides similar to known Na +-channel specific toxins of other scorpions. A new type of peptide was identified with odd number of cysteines (seven), allowing the formation of heterodimers with molecular masses in the range of 16,000 atomic mass units (a.m.u.

Peptides, 2012

Androctonus crassicauda is one of the Southeastern Anatolian scorpions of Turkey with ethno-medic... more Androctonus crassicauda is one of the Southeastern Anatolian scorpions of Turkey with ethno-medical and toxicological importance. Two toxic peptides (Acra1 and Acra2) were isolated and characterized from the venom of this scorpion. In this communication, the isolation of an additional toxin (Acra3) by chromatographic separations (HPLC and TSK-gel sulfopropyl) and its chemical and functional characterization is reported. Acra3 is a 7620Da molecular weight peptide, with 66 amino acid residues crosslinked by four disulfide bridges. The gene coding for this peptide was cloned and sequenced. Acra3 is anticipated to undergo post-translational modifications at the C-terminal region, having an amidated serine as last residue. Injection of Acra3 induces severe neurotoxic events in mice, such as: excitability and convulsions, leading to the death of the animals within a few minutes after injection. Electrophysiological assays conducted with pure Acra3, using cells that specifically expressed sodium channels (Nav1.1-Nav1.6) showed no clear effect. The exact molecular target of Acra3 remained undiscovered, similar to three other scorpion peptides that clustered very closely in the phylogenetic tree included here. The exact target of these four peptides is not very clear.

Journal of Enzyme Inhibition and Medicinal Chemistry, 2013

Abstract In this study, protease-producing capacity of Bacillus pumilus D3, isolated from hydroca... more Abstract In this study, protease-producing capacity of Bacillus pumilus D3, isolated from hydrocarbon contaminated soil, was evaluated and optimized. Optimum growing conditions for B. pumilus D3 in terms of protease production were determined as 1% optimum inoculum size, 35 °C temperature, 11 pH and 48 h incubation time, respectively. Stability studies indicated that the mentioned protease was stable within the pH range of 7-10.5 and between 30 °C and 40 °C temperatures. Surprisingly, the activity of the enzyme increased in the presence of SDS with concentration up to 5 mM. The protease was concentrated 1.6-fold with ammonium sulfate precipitation and dialysis. At least six protein bands were obtained from dialysate by electrophoresis. Four clear protein bands with caseinolytic activity were detected by zymography. Dialysate was further purified by anion-exchange chromatography and the caseinolytic active fraction showed a single band between 29 and 36 kDa of reducing conditions.

Cell Biochemistry and Function, 2006

To evaluate chronic ethanol toxicity on erythrocyte membrane and preventive action of betaine as ... more To evaluate chronic ethanol toxicity on erythrocyte membrane and preventive action of betaine as a methyl donor, 24 male Wistar albino rats were divided into three groups: control, ethanol and ethanol plus betaine group. Animals were fed 60 ml diet per day for two months. Rats in the ethanol group were fed ethanol 8 g/kg/day. The ethanol þ betaine groups were fed ethanol plus betaine (0.5% w/v). After two months, all animals were killed. Malondialdehyde (MDA) and sialic acid (SA) levels were determined in plasma samples. Osmotic fragility tests were performed on whole blood samples and erythrocyte membrane thiol contents were determined using membrane suspensions. Plasma MDA levels in ethanol-given rats were increased significantly compared to the control group of rats (p < 0.05). MDA in the betaine group was significantly lower than that in the ethanol group (p < 0.05). Erythrocyte membrane thiol contents in ethanol group were decreased compared with those of the control group (p < 0.05). Thiol contents were increased slightly after betaine therapy, but this increase was not statistically significant (p > 0.05). Plasma sialic acid levels in the ethanol group were significantly higher than in the control group (p < 0.05). Sialic acid was decreased in the betaine group compared to the ethanol group (p < 0.05). In the osmotic fragility test, we observed that chronic ethanol consumption increased erythrocyte hemolysis. Betaine protected against ethanol-induced hemolysis. Our findings show that chronic ethanol administration affects erythrocyte membrane properties and this may be related to oxidative stress. Betaine protects erythrocyte membrane alterations against chronic ethanol toxicity. Therefore betaine as a nutritional agent, may protect ethanol induced clinical problems associated with membrane abnormalities.

BMC Genomics, 2014

Background: Transcriptome approaches have revealed a diversity of venom compounds from a number o... more Background: Transcriptome approaches have revealed a diversity of venom compounds from a number of venomous species. Mesobuthus gibbosus scorpion showed a medical importance for the toxic effect of its sting. Previously, our group reported the first three transcripts that encode toxin genes in M. gibbosus. However, no additional toxin genes or venom components have been described for this species. Furthermore, only a very small number of reports on the genomic organization of toxin genes of scorpion species have been published. Up to this moment, no information on the gene characterization of M. gibbosus is available. Results: This study provides the first insight into gene expression in venom glands from M. gibbosus scorpion. A cDNA library was generated from the venom glands and subsequently analyzed (301 clones). Sequences from 177 high-quality ESTs were grouped as 48 Mgib sequences, of those 48 sequences, 40 (29 "singletons" and 11 "contigs") correspond with one or more ESTs. We identified putative precursor sequences and were grouped them in different categories (39 unique transcripts, one with alternative reading frames), resulting in the identification of 12 new toxin-like and 5 antimicrobial precursors (transcripts). The analysis of the gene families revealed several new components categorized among various toxin families with effect on ion channels. Sequence analysis of a new KTx precursor provides evidence to validate a new KTx subfamily (α-KTx 27.x). A second part of this work involves the genomic organization of three Meg-chlorotoxin-like genes (ClTxs). Genomic DNA sequence reveals close similarities (presence of one same-phase intron) with the sole genomic organization of chlorotoxins ever reported (from M. martensii). Conclusions: Transcriptome analysis is a powerful strategy that provides complete information of the gene expression and molecular diversity of the venom glands (telson). In this work, we generated the first catalogue of the gene expression and genomic organization of toxins from M. gibbosus. Our result represents a relevant contribution to the knowledge of toxin transcripts and complementary information related with other cell function proteins and venom peptide transcripts. The genomic organization of the chlorotoxin genes may help to understand the diversity of this gene family.

Turkish Journal of …, 2005

The effect of pretreatment on the Pb 2+ biosorption capacity of fungal biomasses, Aspergillus ver... more The effect of pretreatment on the Pb 2+ biosorption capacity of fungal biomasses, Aspergillus versicolor, Metarrhizium anisopliae var. anisopliae, and Penicillium verrucosum, was investigated. For this purpose, the biomasses were subjected to physical treatments such as heat and autoclaving, and chemical treatments such as sodium hydroxide, formaldehyde, gluteraldehyde, acetic acid, hydrogen peroxide, commercial laundry detergent, orthophosphoric acid and dimethyl sulfoxide. Dimethyl sulfoxide, hydrogen peroxide and gluteraldehyde increased biosorption of Pb 2+ in comparison with the A. versicolor live biomass. M. anisopliae var. anisopliae biomass pretreated with hydrogen peroxide, gluteraldehyde, commercial laundry detergent, dimethyl sulfoxide and formaldehyde significantly improved biosorption of Pb 2+ in comparison with live biomass. Pretreatment with all methods of P. verrucosum increased biosorption of Pb 2+ in comparison with live biomass. The maximum biosorption capacity of A. versicolor biomass subjected to dimethyl sulfoxide was 30.6 mg g-1 .

Applied Biochemistry and Biotechnology, 2007

Maltogenic amylases (MAases), a subclass of cyclodextrin (CD)-hydrolyzing enzymes belonging to gl... more Maltogenic amylases (MAases), a subclass of cyclodextrin (CD)-hydrolyzing enzymes belonging to glycoside hydrolase family 13, have been studied extensively, but their physiological roles in microbes and evolutionary relationships with other amylolytic enzymes remain unclear. Here, we report the biochemical properties of a thermostable archaeal MAase from Thermoplasma volcanium GSS1 (TpMA) for the first time. The primary structure and catalytic properties of TpMA were similar to those of MAases, such as possession of an extra domain at its N-terminal and preference for CD over starch. TpMA showed high thermostability and optimal activity at 75°C and 80°C for β-CD and soluble starch, respectively. The recombinant TpMA exists as a high oligomer in a solution and the oligomeric TpMA was dissociated into dimer and monomer mixture by a high concentration of NaCl. The substrate preference and thermostability of TpMA were significantly dependent on the oligomeric state of the enzyme. However, TpMA exhibited distinguishable characteristics from those of bacterial MAases. The transglycosylation pattern of TpMA was opposite to that of bacterial MAases. TpMA formed more α-1,4-glycosidic linked transfer product than α-1,6-linked products. Like as α-amylases, notably, TpMA has a longer subsite structure than those of other CD-degrading enzymes. Our findings in this study suggest that TpMA, the archaeal MAase, shares characteristics of both bacterial MAases and α-amylases, and locates in the middle of the evolutionary process between α-amylases and bacterial MAases.

Trakya Univ J Sci, 2004

... Semra İLHAN, Ahmet ÇABUK, Cansu FİLİK, Figen ÇALIŞKAN Department of Biology, Faculty of Scien... more ... Semra İLHAN, Ahmet ÇABUK, Cansu FİLİK, Figen ÇALIŞKAN Department of Biology, Faculty of Science and Art, Osmangazi University ... Bakır, kurşun ve nikel iyonlarının biyosorpsiyonu üzerine etkisini incelemek üzere, biyokütle ısı ve kimyasal iş-lemlere (sodium hidroksit ...