Purification and N-terminal partial sequence of anti-epilepsy peptide from venom of the scorpion Buthus martensii Karsch

Scorpion Venom Heat–Resistant Synthesized Peptide Increases Stress Resistance and Extends the Lifespan of Caenorhabditis elegans via the Insulin/IGF-1-Like Signal Pathway

Improving healthy life expectancy by targeting aging-related pathological changes has been the spotlight of geroscience. Scorpions have been used in traditional medicine in Asia and Africa for a long time. We have isolated heat-resistant peptides from scorpion venom of Buthusmartensii Karsch (SVHRP) and found that SVHRP can attenuate microglia activation and protect Caenorhabditis elegans (C. elegans) against β-amyloid toxicity. Based on the amino acid sequence of these peptides, scorpion venom heat–resistant synthesized peptide (SVHRSP) was prepared using polypeptide synthesis technology. In the present study, we used C. elegans as a model organism to assess the longevity-related effects and underlying molecular mechanisms of SVHRSP in vivo. The results showed that SVHRSP could prolong the lifespan of worms and significantly improve the age-related physiological functions of worms. SVHRSP increases the survival rate of larvae under oxidative and heat stress and decreases the level of reactive oxygen species and fat accumulation in vivo. Using gene-specific mutation of C. elegans, we found that SVHRSP-mediated prolongation of life depends on Daf-2, Daf-16, Skn-1, and Hsf-1 genes. These results indicate that the antiaging mechanism of SVHRSP in nematodes might be mediated by the insulin/insulin-like growth factor-1 signaling pathway. Meanwhile, SVHRSP could also up-regulate the expression of stress-inducing genes Hsp-16.2, Sod-3, Gei-7, and Ctl-1 associated with aging. In general, our study may have important implications for SVHRSP to promote healthy aging and provide strategies for research and development of drugs to treat age-related diseases.

Antiseizure potential of peptides from the venom of social wasp Chartergellus communis against chemically-induced seizures

Epilepsy is one of the most common neurological diseases in the world. The objective of this research was to investigate a new peptide from the venom of the social wasp Chartergellus communis useful to the study or pharmacotherapy of epilepsy. The wasps were collected, and their venom was extracted. Afterward, the steps of fractionation, sequencing, and identification were carried out to obtain four peptides. These molecules were synthesized for behavioral evaluation tests and electroencephalographic assays to determine their antiseizure potential (induction of acute seizures using the chemical compounds, pentylenetetrazole - PTZ, and pilocarpine - PILO) and analysis of neuropharmacological profile (general spontaneous activity and alteration in motor coordination). Chartergellus-CP1 (i.c.v. - 3.0 μg/animal) caused beneficial alterations in some of the parameters evaluated in both models: PTZ (latency and duration of maximum seizures) and PILO (latency and duration of, and protection against, maximum seizures, and reduction of the median of the seizure scores. When evaluated in 3 doses in the seizure model induced by PILO, the dose of 3.0 μg/animal protected the animals against seizures, with an estimated ED₅₀ of 1.49 μg/animal. Electroencephalographic evaluation of Chartergellus-CP1 showed an improvement in latency, quantity, and percentage of protection against generalized electroencephalographic seizures in the PILO model. Further, Chartergellus-CP1 did not cause adverse effects on general spontaneous activity and motor coordination of animals. This study demonstrated how compounds isolated from wasps' venom may be important resources in the search for new drugs. Such compounds can be considered valuable therapeutic and biotechnological tools for the study and future treatment of epileptic disorders. In this context, a peptide that is potentially useful for epilepsy pharmacotherapy was identified in the venom of C. communis.

BmK NSP, a new sodium channel activator from Buthus martensii Karsch, promotes neurite outgrowth in primary cultured spinal cord neurons

Scorpion venom is a rich source of bioactive compounds that affect neuronal excitability by modulating the activities of various channels/receptors. In the current study, guided by a Ca²⁺ mobilization assay, we purified a new neuroactive peptide designated as BmK NSP (Buthus martensii Karsch neurite-stimulating peptide, MW: 7064.30 Da). The primary structure of BmK NSP was determined by Edman degradation. BmK NSP concentration-dependently elevated intracellular Ca²⁺ concentration ([Ca²⁺]_i) with an EC₅₀ value of 4.18 μM in primary cultured spinal cord neurons (SCNs). Depletion of extracellular Ca²⁺ abolished BmK NSP-triggered Ca²⁺ response. Moreover, we demonstrated that BmK NSP-induced Ca²⁺ response was partially suppressed by the inhibitors of L-type Ca²⁺ channels, Na⁺-Ca²⁺ exchangers and NMDA receptors and was abolished by voltage-gated sodium channel (VGSC) blocker, tetrodotoxin. Whole-cell patch clamp recording demonstrated that BmK NSP delayed VGSC inactivation (EC₅₀ = 1.10 μM) in SCNs. BmK NSP enhanced neurite outgrowth in a non-monotonic manner that peaked at ~30 nM in SCNs. BmK NSP-promoted neurite outgrowth was suppressed by the inhibitors of L-type Ca²⁺ channels, NMDA receptors, and VGSCs. Considered together, these data demonstrate that BmK NSP is a new α-scorpion toxin that enhances neurite outgrowth through main routes of Ca²⁺ influx. Modulation of VGSC activity by α-scorpion toxin might represent a novel strategy to regulate the neurogenesis in SCNs.

Clinical Use of Toxic Proteins and Peptides from Tian Hua Fen and Scorpion Venom

Traditional Chinese Medicine (TCM) has been practiced in China for thousands of years. As a complementary and alternative treatment, herbal medicines that are frequently used in the TCM are the most accepted in the Western world. However, animal materials, which are equally important in the TCM practice, are not well-known in other countries. On the other hand, the Chinese doctors had documented the toxic profiles of hundreds of animals and plants thousand years ago. Furthermore, they saw the potential benefits of these materials and used their toxic properties to treat a wide variety of diseases, such as heavy pain and cancer. Since the 50s of the last century, efforts of the Chinese government and societies to modernize TCM have achieved tremendous scientific results in both laboratory and clinic. A number of toxic proteins have been isolated and their functions identified. Although most of the literature was written in Chinese, this review provide a summary, in English, regarding our knowledge of the clinical use of the toxic proteins isolated from a plant, Tian Hua Fen, and an animal, scorpion, both of which are famous toxic prescriptions in TCM.

Peptides with therapeutic potential in the venom of the scorpion Buthus martensii Karsch

The scorpion Buthus martensii Karsch (BmK) has generated significant interest due to the presence of biologically active peptides in its venom. In the past decade, dozens of different peptides from BmK have been identified. Most of the peptides are neurotoxins and are responsible for the toxicity of BmK venom. Other peptides, including neurotoxins and non-disulfide-bridged peptides, show potential anticancer, antimicrobial, analgesic, and anti-epileptic therapeutic effects. These peptides are attractive candidates for drug development, and peptide derivatives have also been designed to enhance their therapeutic potential, such as ADWX-1 and Kn2-7. In this review, we provide an overview of the most promising peptides found in BmK venom and of modified peptide derivatives showing therapeutic potential.

Chinese Medicine Protein and Peptide in Gene and Cell Therapy

The success of gene and cell therapy in clinic during the past two decades as well as our expanding ability to manipulate these biomaterials are leading to new therapeutic options for a wide range of inherited and acquired diseases. Combining conventional therapies with this emerging field is a promising strategy to treat those previously-thought untreatable diseases. Traditional Chinese medicine (TCM) has evolved for thousands of years in China and still plays an important role in human health. As part of the active ingredients of TCM, proteins and peptides have attracted long-term enthusiasm of researchers. More recently, they have been utilized in gene and cell therapy, resulting in promising novel strategies to treat both cancer and non-cancer diseases. This manuscript presents a critical review on this field, accompanied with perspectives on the challenges and new directions for future research in this emerging frontier.

Arthropod toxins and their antinociceptive properties: From venoms to painkillers

The complex process of pain control commonly involves the use of systemic analgesics; however, in many cases, a more potent and effective polypharmacological approach is needed to promote clinically significant improvement. Additionally, considering side effects caused by current painkillers, drug discovery is once more turning to nature as a source of more efficient therapeutic alternatives. In this context, arthropod venoms contain a vast array of bioactive substances that have evolved to selectively bind to specific pharmacological targets involved in the pain signaling pathway, playing an important role as pain activators or modulators, the latter serving as promising analgesic agents. The current review explores how the pain pathway works and surveys neuroactive compounds obtained from arthropods' toxins, which function as pain modulators through their interaction with specific ion channels and membrane receptors, emerging as promising candidates for drug design and development.

Medical application of scorpion venom to breast cancer: A mini-review

Breast cancer is the leading cause of mortality in women worldwide. Today, 1 in 8 women born in the United States will have an invasive cancer in their lifetime. Despite significant attempts, the prognosis of metastatic breast cancer still remains poor. This has compelled scientists to look elsewhere for better therapeutic outcomes. Recent advances in venomic studies have demonstrated some promise in cancer-related ailments. Scorpion venom, a complex cocktail of biogenic amines, proteins, peptides, mucoproteins, organic salts and neurotoxins has shown a potential therapeutic application due to its cytotoxic, apoptogenic, immunosuppressive and antiproliferative properties. This communication reviews the effects of scorpion venom components on breast cancer and their mechanisms.

Cell-specific expression of the analgesic-antitumor peptide coding sequence under the control of the human α-fetoprotein gene promoter and enhancer

The aim of the present study was to construct a gene-modified hepatocellular carcinoma (HCC)-specific analgesic-antitumor peptide (AGAP) expression vector regulated by the α-fetoprotein (AFP) promoter and enhancer, in order to evaluate its effect. The AFP promoter is generally used in HCC-specific gene therapy strategies. However, this approach is limited by the weak activity of the AFP promoter. Linking the AFP enhancer and promoter has been shown to generate a stronger and more HCC-selective promoter. The AGAP DNA fragment was amplified from the total RNA of the Chinese scorpion, Buthus martensii Karsch. The fragment was subsequently cloned into the pAFP plasmid with the minimal essential DNA fragment, which included the AFP gene promoter and enhancer, to construct the recombinant plasmid, pAFP-AGAP. The plasmid was transfected into HepG2 cells and the mRNA expression levels of AGAP were detected by reverse transcription polymerase chain reaction (RT-PCR). In addition, Cell Counting Kit 8 (CCK-8) was used to analyze the cytotoxicity of plasmid transfection. The length, position and orientation of the inserted AGAP gene were all confirmed to be correct; thus, the recombinant vector was successfully constructed. Using RT-PCR and CCK-8 analysis, the mRNA expression levels of AGAP and the cytotoxicity in AFP-producing human HCC cells were determined. The AFP promoter and enhancer were found to specifically accelerate the expression of the target genes within the cells that were positive for AFP. Therefore, the method used in the present study was demonstrated to be a novel integration of traditional Chinese medicine with western medicine.

Bioactive proteins and peptides isolated from Chinese medicines with pharmaceutical potential

Some protein pharmaceuticals from Chinese medicine have been developed to treat cardiovascular diseases, genetic diseases, and cancer. Bioactive proteins with various pharmacological properties have been successfully isolated from animals such as Hirudo medicinalis (medicinal leech), Eisenia fetida (earthworm), and Mesobuthus martensii (Chinese scorpion), and from herbal medicines derived from species such as Cordyceps militaris, Ganoderma, Momordica cochinchinensis, Viscum album, Poria cocos, Senna obtusifolia, Panax notoginseng, Smilax glabra, Ginkgo biloba, Dioscorea batatas, and Trichosanthes kirilowii. This article reviews the isolation methods, molecular characteristics, bioactivities, pharmacological properties, and potential uses of bioactive proteins originating from these Chinese medicines.

Toxin diversity revealed by a transcriptomic study of Ornithoctonus huwena

Spider venom comprises a mixture of compounds with diverse biological activities, which are used to capture prey and defend against predators. The peptide components bind a broad range of cellular targets with high affinity and selectivity, and appear to have remarkable structural diversity. Although spider venoms have been intensively investigated over the past few decades, venomic strategies to date have generally focused on high-abundance peptides. In addition, the lack of complete spider genomes or representative cDNA libraries has presented significant limitations for researchers interested in molecular diversity and understanding the genetic mechanisms of toxin evolution. In the present study, second-generation sequencing technologies, combined with proteomic analysis, were applied to determine the diverse peptide toxins in venom of the Chinese bird spider Ornithoctonus huwena. In total, 626 toxin precursor sequences were retrieved from transcriptomic data. All toxin precursors clustered into 16 gene superfamilies, which included six novel superfamilies and six novel cysteine patterns. A surprisingly high number of hypermutations and fragment insertions/deletions were detected, which accounted for the majority of toxin gene sequences with low-level expression. These mutations contribute to the formation of diverse cysteine patterns and highly variable isoforms. Furthermore, intraspecific venom variability, in combination with variable transcripts and peptide processing, contributes to the hypervariability of toxins in venoms, and associated rapid and adaptive evolution of toxins for prey capture and defense.

Scorpion venoms as a potential source of novel cancer therapeutic compounds

Scorpions and their venoms have been used in traditional medicine for thousands of years in China, India and Africa. The scorpion venom is a highly complex mixture of salts, nucleotides, biogenic amines, enzymes, mucoproteins, as well as peptides and proteins (e.g. neurotoxins). One of the recently observed biological properties of animal venoms and toxins is that they possess anticancer potential. An increasing number of studies have shown that scorpion venoms and toxins can decrease cancer growth, induce apoptosis and inhibit cancer progression and metastasis in vitro and in vivo. Several active molecules with anticancer activities, ranging from inhibition of proliferation and cell cycle arrest to induction of apoptosis and decreasing cell migration and invasion, have been isolated from scorpion venoms. These observations have shed light on the application of scorpion venoms and toxins as potential novel cancer therapeutics. This mini-review focuses on the anticancer potential of scorpion venoms and toxins and the possible mechanisms for their antitumor activities.

Antinociceptive effects of analgesic-antitumor peptide (AGAP), a neurotoxin from the scorpion Buthus martensii Karsch, on formalin-induced inflammatory pain through a mitogen-activated protein kinases-dependent mechanism in mice

In the present study, we investigated the anti-nociceptive effect and the underlying mechanism of the analgesic-antitumor peptide (AGAP), a neurotoxin from the scorpion Buthus martensii Karsch. AGAP in doses of 0.2, 1 and 5 µg was injected intraplantarly (i.pl.) before formalin injection 10 min at the same site. The suppression by intraplantar injection of AGAP on formalin-induced spontaneous nociceptive behaviors was investigated. The results show that AGAP could dose-dependently inhibit formalin-induced two-phase spontaneous flinching response. To investigate the mechanism of action of treatment with AGAP in inflammatory pain, the expressions of peripheral and spinal phosphorylated mitogen-activated protein kinases (phospho-MAPKs) including p-p38, p-ERK and p-JNK were examined. We found that formalin increased the expressions of peripheral and spinal MAPKs, which were prevented by pre-intraplantar injection of AGAP in inflammation pain model in mice. AGAP could also decrease the expression of spinal Fos induced by formalin. Furthermore, combinations the lower doses of the inhibitors of MAPKs (U0126, SP600125, or SB203580 0.1 µg) with the lower dose of AGAP (0.2 µg), the results suggested that AGAP could potentiate the effects of the inhibitors of MAPKs on the inflammatory pain. The present results indicate that pre-intraplantar injection of AGAP prevents the inflammatory pain induced by formalin through a MAPKs-mediated mechanism in mice.

The expression of analgesic-antitumor peptide (AGAP) from Chinese Buthus martensii Karsch in transgenic tobacco and tomato

The present study aimed to obtain analgesic-antitumor peptide (AGAP) gene expression in plants. The analgesic-antitumor peptide (AGAP) gene was from the venom of Buthus martensii Karsch. Previous studies showed that AGAP has both analgesic and antitumor activities, suggesting that AGAP would be useful in clinical situations as an antitumor drug. Given that using a plant as an expression vector has more advantages than prokaryotic expression, we tried to obtain transgenic plants containing AGAP. In the present study, the AGAP gene was cloned into the plasmid pBI121 to obtain the plant expression vector pBI-AGAP. By tri-parental mating and freeze-thaw transformation, pBI-AGAP was transformed into Agrobacterium tumefaciens LBA4404. Tobacco (Nicotiana tabacum) and tomato (Lycopersicom esculentum) were transformed by the method of Agrobacterium-mediated leaf disc transformation. The transformants were then screened to grow and root on media containing kanamycin. Finally, transformations were confirmed by analysis of PCR, RT-PCR and western blotting. The results showed that the AGAP gene was integrated into the genomic DNA of tobacco and tomato and was successfully expressed. Therefore, the present study suggests a potential industrial application of AGAP expressed in plants.

Eukaryotic expression and purification of anti-epilepsy peptide of Buthus martensii Karsch and its protein interactions

The Asian scorpion Buthus martensil Karsch is important in the Chinese traditional medicine where it is used for the treatment of some nervous system diseases. The anti-epilepsy peptide (AEP) is a 61-amino-acid polypeptide extracted from the venom of B. martensil Karsch. Research has confirmed that it has anti-epileptic effects on the rat model of epilepsy. In this experiment, a cDNA library of AEP from the venom of B. martensil Karsch was constructed using RT-PCR; the primer was designed and used for the amplification. An expression vector of AEP was constructed using Pichia pastoris. Vector expression was induced, and protein purification was then performed. Bolting of the interaction molecule of AEP was by His pull down. Experimental results indicate high AEP expression, and the obtained protein was purified and compared with the control group. Four conspicuous protein bands were observed, and mass chromatographic analysis indicated that the four proteins were synaptosomal-associated protein of 25 kDa (SNAP-25), glial fibrillary acidic protein (GFAP), Glutamic acid decarboxylase (GAD) and N-methyl-D: -aspartate (NMDA). Further, the four protein bands were verified by mammalian two-hybrid experiments and co-immunoprecipitation. AEP was found to interact with SNAP2 and NMDA. This provides experimental evidence for the mechanism of AEP's anti-epileptic action and for the manufacture of a novel type anti-epileptic drug.

Identification of ssDNA aptamers specific for anti-neuroexcitation peptide III and molecular modeling studies: insights into structural interactions

Twelve ssDNA aptamers specific for a novel recombinant anti-neuroexcitation peptide (ANEPIII) were identified using the SELEX method from a 79-nucleotide ssDNA pool to purify ANEPIII in a more efficient way. To further understand the binding modes between ssDNA and ANEPIII, fully flexible dinucleotides were docked onto the homology-modeled ANEPIII structure. AutoDocking identified favorable binding sites on ANEPIII for nucleotides, which was valuable for designing more potent ligands.

Neurotoxins from invertebrates as anticonvulsants: From basic research to therapeutic application

Invertebrate venoms have attracted considerable interest as a potential source of bioactive substances, especially neurotoxins. These molecules have proved to be extremely useful tools for the understanding of synaptic transmission events, and they have contributed to the design of novel drugs for the treatment of neurological disorders and pain. In this context, as epilepsy involves neuronal substrates, which are sites of action of many neurotoxins; venoms may be particularly useful for antiepileptic drug (AED) research. Epilepsy is a chronic disease whose treatment consists of controlling seizures with antiepileptics that very often induce strong undesirable side effects that may limit treatment. Here, we review the vast, but yet unexplored, world of neurotoxins from invertebrates used as probes in pharmacological screening for novel and less toxic antiepileptics. We briefly review (1) the molecular basis of epilepsy, as well as the sites of action of commonly used anticonvulsants (we bring a comprehensive review of the elements from invertebrate venoms which are mostly studied in neuroscience research and may be useful for drug development); (2) peptides from conus snails; (3) peptides and polyamine toxins from spiders and wasps; and (4) peptides from scorpions.

Rat epileptic seizures evoked by BmK αIV and its possible mechanisms involved in sodium channels

This study showed that rat unilateral intracerebroventricular injection of BmK alphaIV, a sodium channel modulator derived from scorpion Buthus martensi Karsch, induced clusters of spikes, epileptic discharges and convulsion-related behavioral changes. BmK alphaIV potently promoted the release of endogenous glutamate from rat cerebrocortical synaptosomes. In vitro examination of the effect of BmK alphaIV on intrasynaptosomal free calcium concentration [Ca(2+)](i) and sodium concentration [Na(+)](i) revealed that BmK alphaIV-evoked glutamate release from synaptosomes was associated with an increase in Ca(2+) and Na(+) influx. Moreover, BmK alphaIV-mediated glutamate release and ion influx was completely blocked by tetrodotoxin, a blocker of sodium channel. Together, these results suggest that the induction of BmK alphaIV-evoked epileptic seizures may be involved in the modulation of BmK alphaIV on tetrodotoxin-sensitive sodium channels located on the nerve terminal, which subsequently enhances the Ca(2+) influx to cause an increase of glutamate release. These findings may provide some insight regarding the mechanism of neuronal action of BmK alphaIV in the central nervous system for understanding epileptogenesis involved in sodium channels.

Development of an improved preparation and an enzyme-linked immunosorbent assay for anti-neuroexcitation peptide (ANEP)

Anti-neuroexcitation peptide (ANEP) is a novel recombinant peptide obtained from the venom of the Chinese scorpion Buthus martensii Karsch. However, the expression of recombinant ANEP in Escherichia coli results in the formation of insoluble aggregates known as inclusion bodies. Here, we describe a novel method for the preparation of ANEP which maximizes the yields of recombinant peptide in a soluble and active form. A non-fusion expression plasmid pNJUTRX-1-ANEP-His(6) encoding recombinant ANEP with a His(6)-tag at its C-terminus was constructed and transformed into E. coli strain BL21 (DE3). The expressed ANEP was almost in soluble form and accounted for about 12% of the total cellular proteins. The recombinant ANEP in the cell lysate was purified to homogeneity by His Bind affinity chromatography. This effective method solved the problem of a lack of sufficient active peptide which, until now, has hampered the further research and development. In order to develop an immunoassay method for ANEP, polyclonal rabbit antiserum was raised against the prepared ANEP and purified by protein A affinity chromatography. It was confirmed that the antibody reacted with recombinant ANEP by both Western blotting and ELISA results. Using purified antibody, the immunoassay method was developed.

Cloning and characterization of a novel calcium channel toxin-like gene BmCa1 from Chinese scorpion Mesobuthus martensii Karsch

Many studies have been carried on peptides and genes encoding scorpion toxins from the venom of Mesobuthus martensii Karsch (synonym: Buthus martensii Karsch, BmK), such as Na+, K+ and Cl- channel modulators. In this study, a novel calcium channel toxin-like gene BmCa1 was isolated and characterized from the venom of Mesobuthus martensii Karsch. First, a partial cDNA sequence of the Ca2+ channel toxin-like gene was identified by random sequencing method from a venomous gland cDNA library of Mesobuthus martensii Karsch. The full-length sequence of BmCa1 was then obtained by 5'RACE technique. The peptide deduced from BmCa1 precursor nucleotide sequence contains a 27-residue signal peptide and a 37-residue mature peptide. Although BmCa1 and other scorpion toxins are different at the gene and protein primary structure levels, BmCa1 has the same precursor nucleotide organization and cysteine arrangement as that of the first subfamily members of calcium channel scorpion toxins. Genomic DNA sequence of BmCa1 was also cloned by PCR. Sequence analysis showed that BmCa1 gene consists of three exons separated by two introns of 72 bp and 1076 bp in length, respectively. BmCa1 is the first calcium channel toxin-like gene cloned from the venom of Mesobuthus martensii Karsch and potentially represents a novel class of calcium channel toxins in scorpion venoms.

ANEPIII, a new recombinant neurotoxic polypeptide derived from scorpion peptide, inhibits delayed rectifier, but not A-type potassium currents in rat primary cultured hippocampal and cortical neurons

A new recombinant neurotoxic polypeptide ANEPIII (BmK ANEPIII) derived from Scorpion peptide, which was demonstrated with antineuroexcitation properties in animal models, was examined for its action on K+ currents in primary cultured rat hippocampal and cortical neurons using the patch clamp technique in the whole-cell configuration. The delayed rectifier K+ current (I(k)) was inhibited by externally applied recombinant BmK ANEPIII, while the transient A-current (I(A)) remained virtually unaffected. BmK ANEPIII 3 microM, reduced the delayed rectifier current by 28.2% and 23.6% in cultured rat hippocampal and cortical neurons, respectively. The concentration of half-maximal block was 155.1 nM for hippocampal neurons and 227.2 nM for cortical neurons, respectively. These results suggest that BmK ANEPIII affect K+ currents, which may lead to a reduction in neuronal excitability.

Molecular cloning of a novel putative potassium channel-blocking neurotoxin from the venom of the North African scorpion, Androctonus amoreuxi

Scorpion venoms are a particularly rich source of neurotoxic proteins/peptides that interact in a highly specific fashion with discrete subtypes of ion channels in excitable and non-excitable cells. Here we have employed a recently developed technique to effect molecular cloning and structural characterization of a novel putative potassium channel-blocking toxin from the same sample of venom from the North African scorpion, Androctonus amoreuxi. The deduced precursor open-reading frame is composed of 59 amino acid residues that consists of a signal peptide of approximately 22 amino acid residues followed by a mature toxin of 37 amino acid residues. The mature toxin contains two functionally important residues (Lys27 and Tyr36), constituting a functional dyad motif that may be critical for potassium channel-blocking activity that can be affirmed from structural homologs as occurring in the venoms from other species of Androctonus scorpions. Parallel proteomic/transcriptomic studies can thus be performed on the same scorpion venom sample without sacrifice of the donor animal.

Neuroprotection and peptide toxins

Neurodegeneration induced by excitatory neurotransmitter glutamate is considered to be of particular relevance in several types of acute and chronic neurological impairments ranging from cerebral ischaemia to neuropathological conditions such as motor neuron disease, Alzheimer's, Parkinson's disease and epilepsy. The hyperexcitation of glutamate receptors coupled with calcium overload can be prevented or modulated by using well-established competitive and non-competitive antagonists targeting ion/receptor channels. The exponentially increasing body of pharmacological evidence over the years indicates potential applications of peptide toxins, due to their exquisite subtype selectivity on ion channels and receptors, as lead structures for the development of drugs for the treatment of wide variety of neurological disorders. This review comprehensively highlights the overview of the diversity in the molecular as well as neurobiological mechanisms of different peptide toxins derived from venomous animals with particular reference to neuroprotection. In addition, the potential applications of peptide toxins in the diagnosis and treatment of neurological disorders such as neuromuscular disorders, epilepsy, Alzheimer's and Parkinson's diseases, gliomas and ischaemic stroke and their future prospects in the diagnosis as well as in the therapy are addressed.

Isolation of scorpion (Androctonus amoreuxi) putative alpha neurotoxins and parallel cloning of their respective cDNAs from a single sample of venom

The venoms of buthid scorpions are known to contain basic, single-chain protein toxins (alpha toxins) consisting of 60-70 amino acid residues that are tightly folded by four disulfide bridges. Here we describe isolation and sequencing of three novel putative alpha toxins (AamH1-3) from the venom of the North African scorpion, Androctonus amoreuxi, and subsequent cloning of their precursor cDNAs from the same sample of venom. This experimental approach can expedite functional genomic analyses of the protein toxins from this group of venomous animals and does not require specimen sacrifice for cloning of protein toxin precursor cDNAs.

Expression of an antitumor-analgesic peptide from the venom of Chinese scorpion Buthus martensii karsch in Escherichia coli

The gene encoding a putative mature antitumor-analgesic peptide (AGAP) from the venom of the Chinese scorpion Buthus martensii Karsch was obtained by polymerase chain reaction (PCR) according to its cDNA sequence and expressed in Escherichia coli. While most of the recombinant AGAP was expressed in the form of insoluble inclusion body. The recombinant AGAP was purified to homogeneity by metal chelating affinity chromatography. Pharmaceutical tests showed that the recombinant AGAP has both analgesic and antitumor activities on mice.

c-Fos expression in rat spinal cord induced by scorpion BmK venom via plantar subcutaneous injection

The aim of this study was to assess the cell-type and distribution of highly activated neurons in rat spinal cord underlying nociceptive responses induced by scorpion BmK venom using Fos immunohistochemistry. BmK venom was intraplantarly injected into one hind paw of a conscious rat. Fos-like immunoreactive neurons were found to predominantly distribute at L4-5 segments in the rat spinal cord after BmK venom application. c-Fos labeling was most dense in the medial half portion of laminae I-II, moderately dense in laminae V-VI and less dense in laminae III-IV, VII-X. c-Fos labeling could be detected at 0.5 h, reached the peak at 2 h, decreased steeply from 4 h and then almost disappeared at 24 h. Ten to fifty micrograms of BmK venom was deemed to be a sufficient dosage to evoke c-Fos expression. On the other hand, c-Fos expression induced by BmK venom could be suppressed partially by systemic morphine in a dose-dependent manner. The results suggest that the different extent of activities of neuronal subpopulation in the spinal cord involved in nociceptive transmission manifesting as c-Fos expression, were mainly correlated with mechanisms underlying the generation, maintenance and/or modulation of spontaneous pain and hyperalgesia evoked by BmK venom.

Isolation, purification, and N-terminal partial sequence of an antitumor peptide from the venom of the Chinese scorpion Buthus martensii Karsch

An antitumor peptide (ANTP) was isolated and purified from the venom of the Chinese scorpion Buthus martensii Karsch. The purification procedure included gel filtration on Sephadex G-50 and Superdex 30 high resolution chromatography, Phenyl Sepharose 6 Fast Flow chromatography, and SP-Sepharose Fast Flow chromatography. Its homogeneity was demonstrated by size exclusion HPLC on TSK G2000 SW. The isoelectric point is more than 10 by pH 3-10 range isoelectric focusing. ANTP has a relative molecular mass of 6280, calculated from the measurement of 16.5% SDS-PAGE. The pharmacological tests showed that ANTP has antitumoral effects in the mouse S-180 fibrosarcoma model and Ehrlich ascites tumor model. Amino acid analysis suggested the ANTP is rich in glycine and does not have histidine and threonine. The sequence of the first 25 N-terminal residues is as follows: Val-Arg-Asp-Gly-Tyr-Ile-Ala-Asp-Asp-Lys-Asn-Cys-Ala-Tyr-Phe-Cys-Gly-Arg-Asn-Ala-Tyr-Cys-Asp-Asp-Glu.

An overview of toxins and genes from the venom of the Asian scorpion Buthus martensi Karsch

Among the different scorpion species, Buthus martensi Karsch (BmK), a widely distributed scorpion species in Asia, has received a lot of attention. Indeed, over the past decade, more than 70 different peptides, toxins or homologues have been isolated and more peptides are probably still to be revealed. This review is focusing on the many peptides isolated from the venom of this scorpion, their targets, their genes and their structures. The aim is to give both a 'state of the art' view of the research on BmK venom and an illustration of the complexity of this scorpion venom. In the present manuscript, we have listed the different ion channel toxins and homologues isolated from the venom of BmK, either from the literature or from databases. We have described here 51 long-chain peptides related to the Na(+) channel toxins family: 34 related to the alpha-toxin family, four related to the excitatory insect toxin family, 10 related to the depressant insect toxin, one beta-like toxin plus two peptides, BmK AS and AS1, that act on ryanodine receptors. We also listed 18 peptides related to the K(+) channel toxin family: 14 short chain toxins or homologues, two long chain K(+) toxin homologues and two putative K(+) toxin precursors. Additionally, two chlorotoxin like peptides (Bm-12 and 12 b) have been isolated in the venom of BmK. Besides these ion channels toxins, two peptides without disulfide bridges (the bradykinin-potentiating peptide BmK bpp and BmK n1) and three peptides with no known functions have also been discovered in this venom. We have also taken the opportunity of this review to update the classification of scorpion K(+) toxins () which now presents 17 subfamilies instead of the 12 described earlier. The work on the venom of BmK led to the discovery of two new subfamilies, alpha-KT x 14 and alpha-KT x 17.

Molecular cloning and functional expression of a gene encoding an antiarrhythmia peptide derived from the scorpion toxin

From a cDNA library of Chinese scorpion Buthus martensii Karsch, full-length cDNAs of 351 nucleotides encoding precursors (named BmKIM) that contain signal peptides of 21 amino acid residues, a mature toxin of 61 residues with four disulfide bridges, and an extra Gly-Lys-Lys tail, were isolated. The genomic sequence of BmKIM was cloned and sequenced; it consisted of two exons disrupted by an intron of 1622 bp, the largest known in scorpion toxin genomes, inserted in the region encoding the signal peptide. The cDNA was expressed in Escherichia coli. The recombinant BmKIM was toxic to both mammal and insects. This is the first report that a toxin with such high sequence homology with an insect-specific depressant toxin group exhibits toxicity to mammals. Using whole cell patch-clamp recording, it was discovered that the recombinant BmKIM inhibited the sodium current in rat dorsal root ganglion neurons and ventricular myocytes and protected against aconitine- induced cardiac arrhythmia.

Dynamic determination and possible mechanism of amino acid transmitter release from rat spinal dorsal horn induced by the venom and a neurotoxin (BmK I) of scorpion Buthus martensi Karsch

In the present communication, we determined the dynamic release of amino acid transmitters from spinal dorsal horn induced by scorpion Buthus martensi Karsch (BmK) venom and a neurotoxin (BmK I). The results found that glutamate and aspartate release could be evoked significantly within the initial 30 min with the applied doses of either 0.05 and 0.01 mg BmK venom or 0.01 and 0.002 mg BmK I. However, gamma-aminobutyric acid (GABA) release could be largely evoked during the second 30 min by the venom, but not by BmK I. The result suggested that nociceptive afferent fibers could be activated to induce excitatory amino acid release from spinal dorsal horn by nociceptive factors such as BmK I, but the delayed release of GABA might be attributed to the modulating role of some antinociceptive components in the venom.

A depressant insect toxin with a novel analgesic effect from scorpion Buthus martensii Karsch

A new peptide named BmK dITAP3 from scorpion Buthus martensii Karsch (BmK) has been identified to possess a dual bioactivity, a depressant neurotoxicity on insects and an analgesic effect on mice. The bioassays also showed that the peptide was definitely devoid of the neurotoxicity on mammals, which indicated that the analgesic effect of BmK dITAP3 could not be ascribed to the syndromic effects of a mammalian neurotoxicity. BmK dITAP3 exhibited 43.0% inhibition efficiency of the analgesic effect on mice at a dose of 5 mg/kg and the FPU value of 0.5 microg/body (approximately 30 mg) on the fly larvae. The pI value and the molecular mass determined by MALDI-TOF MS for dITAP3 were 6.5 and 6722.7, respectively. Its first 15 N-terminal residues were determined by Edman degradation, based on which the full amino acid sequence was deduced from the cDNA sequence encoding the peptide with 3'-RACE. Circular dichroism and sequence based prediction analyses showed dITAP3 may have a similar molecular scaffold as the most scorpion toxins but with features of the more beta structures and much less of alpha helix. The details of the purification, characterization and sequencing as well as the sequence comparison with other depressant insect toxins and the correlation between the analgesic effect and the insect toxicity will be reported and discussed, respectively.

Purification, characterization, and primary structure of four depressant insect-selective neurotoxin analogs from scorpion (Buthus sindicus) venom

Four depressant insect-selective neurotoxin analogs (termed Bs-dprIT1 to 4) from the venom of the scorpion Buthus sindicus were purified to homogeneity in a single step using reverse-phase HPLC. The molecular masses of the purified toxins were 6820.9, 6892.4, 6714.7, and 6657.1 Da, respectively, as determined by mass spectrometry. These long-chain neurotoxins were potent against insects with half lethal dose values of 67, 81, 103, and 78 ng/100 mg larva and 138, 160, 163, and 142 ng/100 mg cockroach, respectively, but were not lethal to mice even at the highest applied dose of 10 microg/20 g mouse. When injected into blowfly larvae (Sarcophaga falculata), Bs-dprIT1 to 4 induced classical manifestations of depressant toxins, i.e., a slow depressant flaccid paralysis. The primary structures of Bs-dprIT 1 to 4 revealed high sequence homology (60-75%) with other depressant insect toxins isolated from scorpion venoms. Despite the high sequence conservation, Bs-dprIT1 to 4 showed some remarkable features such as (i) the presence of methionine (Met(6) in Bs-dprIT1 and Met(24) in Bs-dprIT2 to 4) and histidine (His(53) and His(57) in Bs-dprIT1) residues, i.e., amino acid residues that are uncommon to this type of toxin; (ii) the substitution of two highly conserved tryptophan residues (Trp43 --> Ala and Trp53 --> His) in the sequence of Bs-dprIT1; and (iii) the occurrence of more positively charged amino acid residues at the C-terminal end than in other depressant insect toxins. Multiple sequence alignment, sequence analysis, sequence-based structure prediction, and 3D homology modeling studies revealed a protein fold and secondary structural elements similar to those of other scorpion toxins affecting sodium channel activation. The electrostatic potential calculated on the surface of the predicted 3D model of Bs-dprIT1 revealed a significant positive patch in the region of the toxin that is supposed to bind to the sodium channel.

A new insect neurotoxin AngP1 with analgesic effect from the scorpion Buthus martensii Karsch: purification and characterization

An insect toxin named BmK AngP1 was purified from the venom of the scorpion Buthus martensii Karsch (BmK). It also shows an evident analgesic effect on mice, but is interestingly devoid of mammalian toxicity. Bioassay showed that the CPU value of AngP1 was 0.01 microg/body ( approximately 30 mg) for the excitatory insect toxicity and 43.0% inhibition efficiency for analgesia at a dose of 5 mg/kg. However, even at the dosage of 10 mg/kg no detectable toxicity on mice could be found. The isoelectric point (pI) value for AngP1 was 4.0, and its molecular mass analyzed by MALDI-TOF MS was 8141.0. The first 15 N-terminal residues of AngP1 were determined by Edman degradation and showed high similarity to that of other excitatory scorpion insect toxins. The circular dichroism spectroscopy measured on a JASCO J-720 system showed that there were 10.4% alpha-helix, 46.2% beta-strand and 14.1% turn structure in this peptide. Under two conditions single crystals of AngP1 were obtained.

Molecular characterization of an anti-epilepsy peptide from the scorpion Buthus martensi Karsch

For a long time Asian scorpion Buthus martensi Karsch (BmK) has been used in Chinese traditional medicine to cure many diseases of nervous system. Here we report the purification and characterization of a pharmacologically active neurotoxin from the scorpion BmK. This toxin had little toxicity in mice and insects but was found to have an anti-epilepsy effect in rats, and is thus named as BmK anti-epilepsy peptide (BmK AEP). Its amino-acid sequence was determined by lysylendopeptidase digestion, Edman degradation and mass spectrographic analysis. Based on the determined sequence, the gene coding for this peptide was also cloned and sequenced by the 3' and 5' RACE methods. It encodes a precursor of 85 amino-acid residues including a signal peptide of 21 residues, a mature peptide of 61 residues and three additional residues Gly-Lys-Lys at the C-terminus. The additional Gly sometimes followed by one or two basic residues is prerequisite for the amidation of its C-terminus. C-terminal amidation was also verified by the molecular-mass determination of BmK AEP. This anti-epilepsy peptide toxin shares homology with other depressant insect toxins. The remarkable difference between them was mainly focused at residues 6, 7 and 39; these residues might relate to the unique action of BmK AEP.

The inhibitory effects of BmK IT2, a scorpion neurotoxin on rat nociceptive flexion reflex and a possible mechanism for modulating voltage-gated Na(+) channels

Buthus martensi Karsch IT2 (BmK IT2), a scorpion neurotoxin, was found to display a biphasic inhibitory effect on the C component of the rat nociceptive flexion reflex by subcutaneous injection in vivo, and also on the total Na(+) currents of rat dorsal root ganglion neurons using whole-cell patch clamping. BmK IT2 blocked the tetrodotoxin-resistant (TTX-R) component of the Na(+) currents with a degree of selectivity. The partial block of the TTX-R Na(+) currents, brought about by 0.01 microg/microl BmK IT2, reversed less rapidly and completely than the partial block of the tetrodotoxin-sensitive (TTX-S) current brought about by the same concentration of BmK IT2. These results suggest that the inhibition of the rat nociceptive flexion reflex by BmK IT2 may be attributed to modulation of the different voltage-gated Na(+) channels.

Expression of anti-neuroexcitation peptide (ANEP) of scorpion Buthus martensii Karsch in Escherichia coli

According to the cDNA sequence of anti-neuroexcitation peptide of scorpion Buthus martensii Karsch, the putative mature anti-neuroexcitation peptide (ANEP) encoding DNA fragment was obtained by a PCR method, then was cloned into expression plasmid pET28a, fused with His tag at its 3' end. When expressed in E. coli BL21 (DE3), the expression of recombinant ANEP was 15% of total cellular proteins, while most recombinant ANEP products existed in the form of insoluble inclusion bodies. Coexpression of molecular chaperones or protein disulfide isomerase could not improve its solubility. The recombinant ANEP in the cell lysate was purified to homogeneity by metal chelating affinity chromatography and Superdex 30 chromatography. In bioassay with convulsive mice model induced by thiosemicarbazide, recombinant ANEP could apparently delay the convulsion seizure of model animals by 18% and showed anti-neuroexcitatory activity.

Buthus martensi Karsch agonist of skeletal-muscle RyR-1, a scorpion active polypeptide: antinociceptive effect on rat peripheral nervous system and spinal cord, and inhibition of voltage-gated Na(+) currents in dorsal root ganglion neurons

The antinociceptive effect and potential antinociceptive mechanism of Buthus martensi Karsch agonist of skeletal-muscle RyR-1 (BmK AS-1), a scorpion venom derived neurotoxic polypeptide, have been investigated in rats. The results show that: (a) the withdrawal latency to rat plantar radiant heat was increased significantly by 100 and 150% after intrathecal injection of 0.6 and 1.2 microg doses; (b) C components of rat nociceptive flexion reflex were reduced to 72, 50 and 29% after intraplantar injection of 5, 10 and 20 microg doses; (c) both central (spinal cord) and peripheral antinociceptive effects of BmK AS-1 could not be reversed by naloxone; (d) tetrodotoxin-resistant (TTX-R) Na(+) current was depressed to 83.87+/-1.64, 64.73+/-5.43 and 15.85+/-17.63%, and tetrodotoxin-sensitive (TTX-S) Na(+) current was depressed to about 81.27+/-2.5, 49.08+/-8.09 and 9.03+/-12.34% with 0.2, 1.0 and 10 microg/ml BmK AS-1 measured using patch clamp recording in rat small dorsal root ganglion (DRG) neurons, respectively. The results indicate that BmK AS-1 may be a new component with potent antinociceptive activity mediated by modulating TTX-S and TTX-R Na(+) channels.

The binding of BmK IT2, a depressant insect-selective scorpion toxin on mammal and insect sodium channels

Binding assay of (125)I-BmK IT2, a depressant insect-selective scorpion toxin showed two non-interacting binding sites on insect neuronal membranes: a high affinity (K(d(1))=0.65+/-0.20 nM) and low capacity (B(max(1))=0.46+/-0.13 pmol/mg protein) binding site, as well as a low-affinity (K(d(2))=78.7+/-16.4 nM) and high capacity (B(max(2))=33.1+/-8.5 pmol/mg protein) binding site. BmK IT2 could associate with and dissociate from its binding sites on insect neuronal membranes in quick manner (k(1)=5.4 x 10(5) S(-1) M(-1) and k(2)=3.2 x 10(4) S(-1) M(-1); k(-1)=7.4 x 10(-4) S(-1) and k(-2)=5.3 x 10(-3) S(-1)). The binding of (125)I-BmK IT2 to insect synaptosomes could be significantly inhibited by native BmK IT2, BmK AS and BmK AS-1 in a dose-dependent manner, and partially by BmK I, but not modified by depolarization of membrane potential and veratridine, In addition, specific binding of (125)I-BmK IT2 seem to be undetectable on rat brain synaptosomes even at high concentration. Whole cell patch-clamping recording found that BmK IT2 could partially inhibit total sodium currents of rat DRG neurons, the inhibitory effects were reversible. The results suggest that the receptor binding site of BmK IT2 on insect sodium channels might be similar to that on sodium channels of mammal peripheral nervous system, but different from that of mammal central nervous system.

Antihyperalgesia effect of BmK IT2, a depressant insect-selective scorpion toxin in rat by peripheral administration

The study was undertaken to assess the antihyperalgesia effect of BmK IT2, a sodium channel-specific ligand purified from the venom of Chinese scorpion Buthus martensi Karsch in rat by peripheral injection. The peripheral inflammation of rat was induced by carrageenan resulted in hyperalgesia to heat stimulus. The heat hyperalgesia was measured by paw withdrawal latency (PWL). PWL was increased to 272 +/- 18%, 217 +/- 19% and 186 +/- 16% of the control by application of 10 microl BmK IT2 at the concentration of 0.1, 0. 01 and 0.001 mg/ml in inflammatory rats, respectively. In contrast, PWL was enhanced to about 177 +/- 16%, 141 +/- 15% and 133 +/- 15% of the control at the same applied concentrations of BmK IT2 in normal rats. The results thus suggest that BmK IT2 can produce peripheral antihyperalgesia and antinociception, which might be attributed a pathway of modulating the sodium channels on nociceptor.

Molecular characterization of a new excitatory insect neurotoxin with an analgesic effect on mice from the scorpion Buthus martensi Karsch

Besides the neurotoxins active on mammals, a new excitatory insect selective toxin with a mice analgesic activity was found and purified from the venom of the scorpion Buthus martensi Karsch (BmK) (Ji, Y.H., Mansuelle, P., Terakawa, S., Kopeyan, C., Yanaihara, N., Hsu, K., Rochat, H., 1996. Toxicon 34, 987; Luo, M.J., Xiong, Y.M., Wang, M., Wang, D.C., Chi, C.W., 1997. Toxicon 35, 723.). This peptide (designated as BmK IT-AP) is composed of 72 amino acid residues. Its primary structure was determined by automated Edman degradation of the N-terminal part of the reduced and S-carboxamidemethylated protein and its lysylendopeptidase degraded fragments. Based on the determined sequence, the gene specific primers were designed and synthesized for 3' and 5' RACE (rapid amplification of cDNA ends). Their partial cDNA fragments obtained by 3' and 5' RACEwere cloned and sequenced and the full length cDNA sequence of BmK IT-AP was then completed by overlapping their two partial cDNA sequences. It encodes a precursor of 90 amino acid residues: a signal peptide of 18 residues and a mature peptide of 72 residues which are consistent with the determined protein sequence of BmK IT-AP. The genomic DNA of the peptide was also amplified by PCR from the scorpion genomic DNA and sequenced, which is a first report on the genomic structure of a scorpion toxin specific for insects. Its sequence revealed an intron of 590 bp inserted in the end part of the signal peptide. The peptide caused a fast excitatory contraction paralysis on house fly larvae. Furthermore, the peptide also showed an obvious analgesic effect on mice, as assayed by using a twisting test model. This effect of BmK IT-AP well characterized at molecular level is first reported among the known scorpion insect neurotoxins.

Behavioral, electroencephalographic, and histopathologic effects of a neuropeptide isolated from Tityus serrulatus scorpion venom in rats

The effects of intrahippocampal administration of a neuropeptide (TS-8F toxin) isolated from Tityus serrulatus scorpion venom have been determined on behavior, limbic seizures, and neuronal degeneration in rats. Behavioral observation showed orofacial automatism, wet dog shakes, and myoclonus. Concomitantly, the electroencephalographic record showed high-frequency and high-voltage spikes that evolved to seizure activity in the hippocampus and cortex. Seven days after TS-8F toxin microinjection, neuronal damage was observed in CA1 and CA2 pyramidal cells and in granular cells of the dentate gyrus. The results suggest that TS-8F toxin may be responsible, at least in part, by the epileptic effects observed with the crude venom. Thus, this toxin may be a useful tool in the study of some neurobiological process.

The CDNA and genomic DNA sequences of a mammalian neurotoxin from the scorpion Buthus martensii Karsch

The cDNA library of venomous glands of the scorpion Buthus martensii Karsch (BmK) was constructed. A cDNA encoding a mammalian neurotoxin corresponding to the known alpha-type toxin, BmK M1, was amplified by polymerase chain reaction (PCR) and cloned, and its full-length sequence was determined. The open reading frame encoded the precursor of BmK M1 with 84 amino acid residues, including a signal peptide of 19 residues, a mature toxin of 64 residues and an additional C-terminal residue Arg which might be cleaved off by proteinase postprocessing immediately after protein synthesis. Based on the determined cDNA sequence and using the total DNA of the scorpion as a template, the gene of BmK M1 was also amplified by PCR and sequenced. The genomic DNA sequence revealed an intron of 408 base pairs present within the signal peptide region. Both the intron and exon of BmK M1 share about 75% similarity with those of AaH I' another alpha-type mammalian neurotoxin in the scorpion Androctonus australis Hector.

Purification, N-terminal sequence and structural characterization of a toxic protein from the Indian scorpion venom Buthus tamulus

A toxic protein component (Bt-II) was isolated from the venom of the Indian scorpion, Buthus tamulus, by ion-exchange chromatography on Biorex-70 and reverse phase high pressure liquid chromatography (RP-HPLC). This 7800 mol. wt protein was found to have an LD50 value of 2.25 mg/kg body weight in mice by subcutaneous injection. Amino acid composition of the protein revealed the presence of aromatic and basic amino acids; the N-terminal amino acid sequence was also determined. Structural characterization of Bt-II, based on circular dichroic and fluorescent quenching studies, has also been reported.

Purification of outer membrane iron transport receptors from Escherichia coli by fast protein liquid chromatography: FepA and FecA

Fast protein liquid chromatography (FPLC) with DEAE-Sepharose Fast Flow, PBE-94 and Q-Sepharose Fast Flow columns are applied to the purification of the ferric enterobactin protein receptor (FepA). The apparent single band of FepA on SDS-PAGE is isolated and purified into two proteins with very similar molecular weights. The two proteins are identified to be FepA and ferric citrate protein receptor (FecA) by N-terminus amino acid determination and a computer search with the Gene Bank file. The assay of binding activities of these proteins shows that both FepA and FecA bind ferric enterobactin, with the former having about double the activity of the latter. Competition studies shows that Fe-MECAM is competitively bound to both proteins and that ferric parabactin only slightly competes with [55Fe]ferric enterobactin. It is found that ferrichrome A has no effect on the binding of the receptor proteins with ferric enterobactin.