Expression of a group II phospholipase A2 from the venom of Agkistrodon piscivorus piscivorus in Escherichia coli: recovery and renaturation from bacterial inclusion bodies

The allelopathic potential of red macroalga Pyropia haitanensis solvent extracts on controlling bloom-forming microalgae: Insights into the inhibitory compounds

Various strategies have been explored to mitigate the impact of harmful algal blooms (HABs). While chemical and physical methods have traditionally been employed to regulate microalgal growth, their prolonged adverse effects on the ecosystem are a cause for concern. Recognizing the integral role of macroalgae within the ecosystem, this study reveals the anti-algal properties of solvent-based extracts derived from the red macroalga Pyropia haitanensis as a means of preventing microalgal blooms. In our investigation, we initially assessed the growth-inhibitory effects of methanol and acetone extracts from P. haitanensis on five microalgae known to contribute to bloom-formation. Significantly reduced growth was observed in all microalgal species when inoculated with both methanol and acetone extracts. Further analysis revealed the effectiveness of the methanol extract (ME), and further fractionation with petroleum ether (PE), ethyl acetate (EA), and n-butanol (NB) for testing against Skeletonema costatum and Pseudo-nitzschia pungens. The methanol fractions exhibited strong inhibition, resulting in the complete elimination of both microalgae after 96 hours of exposure to PE, EA, and NB extracts. Gas Chromatography-Mass Spectroscopy (GC-MS) analysis of the ME and its solvent fractions identified 49 confirmed compounds. These compounds are likely potential contributors to the observed inhibition of microalgal growth. In conclusion, our findings suggest that solvent extracts from P. haitanensis possess substantial potential for the control of HABs, offering a promising avenue for further research and application in ecosystem management.

Structural and functional characterization of a thermostable secretory phospholipase A2 from Sciscionella marina and its application in liposome biotransformation

Secretory phospholipase A₂ (sPLA₂), which hydrolyzes the sn-2 acyl bond of lecithin in a Ca²⁺-dependent manner, is an important enzyme in the oil and oleochemical industries. However, most sPLA₂s are not stable under process conditions. Therefore, a thermostable sPLA₂ was investigated in this study. A marine bacterial sPLA₂ isolated from Sciscionella marina (Sm-sPLA₂) was catalytically active even after 5 h of incubation at high temperatures of up to 50°C, which is outstanding compared with a representative bacterial sPLA₂ (i.e. sPLA₂ from Streptomyces violaceoruber; Sv-sPLA₂). Consistent with this, the melting temperature of Sm-sPLA₂ was measured to be 7.7°C higher than that of Sv-sPLA₂. Furthermore, Sm-sPLA₂ exhibited an improved biotransformation performance compared with Sv-sPLA₂ in the hydrolysis of soy lecithin to lysolecithin and free fatty acids at 50°C. Structural and mutagenesis studies revealed that the Trp41-mediated anchoring of a Ca²⁺-binding loop into the rest of the protein body is directly linked to the thermal stability of Sm-sPLA₂. This finding provides a novel structural insight into the thermostability of sPLA₂ and could be applied to create mutant proteins with enhanced industrial potential.

Expression of Cloned Genes in E. coli Using IPTG-Inducible Promoters

Many Escherichia coli expression vectors make use of the lac operon. In general, the lac operator (lacO) is located downstream from the promoter of the target gene, so that binding of the lac repressor blocks transcription initiation until lactose or the isopropyl-β-d-thiogalactopyranoside (IPTG) analog is added. The protocol given here is intended for use with IPTG-inducible vectors. l-Arabinose-inducible systems derived from the ara operon offer an alternative to expression systems based on the lac operon; guidance for their use is also provided.

Engineering of a Microbial Cell Factory for the Extracellular Production of Catalytically Active Phospholipase A2 of Streptomyces violaceoruber

Phospholipase A2 (PLA2) from Streptomyces violaceoruber is a lipolytic enzyme used in a wide range of industrial applications including production of lysolecithins and enzymatic degumming of edible oils. We have therefore investigated expression and secretion of PLA2 in two workhorse microbes, Pichia pastoris and Escherichia coli. The PLA2 was produced to an activity of 0.517 ± 0.012 U/ml in the culture broth of the recombinant P. pastoris. On the other hand, recombinant E. coli BL21 star (DE3), overexpressing the authentic PLA2 (P-PLA2), showed activity of 17.0 ± 1.3 U/ml in the intracellular fraction and 21.7 ± 0.7 U/ml in the culture broth. The extracellular PLA2 activity obtained with the recombinant E. coli system was 3.2-fold higher than the corresponding value reached in a previous study, which employed recombinant E. coli BL21 (DE3) overexpressing codon-optimized PLA2. Finally, we observed that the extracellular PLA2 from the recombinant E. coli P-PLA2 culture was able to hydrolyze 31.1 g/l of crude soybean lecithin, an industrial substrate, to a conversion yield of approximately 95%. The newly developed E. coli-based PLA2 expression system led to extracellular production of PLA2 to a productivity of 678 U/l·h, corresponding to 157-fold higher than that obtained with the P. pastoris-based system. This study will contribute to the extracellular production of a catalytically active PLA2.

ACP-TX-I and ACP-TX-II, Two Novel Phospholipases A2 Isolated from Trans-Pecos Copperhead Agkistrodon contortrix pictigaster Venom: Biochemical and Functional Characterization

This work reports the purification and biochemical and functional characterization of ACP-TX-I and ACP-TX-II, two phospholipases A₂ (PLA₂) from Agkistrodon contortrix pictigaster venom. Both PLA₂s were highly purified by a single chromatographic step on a C₁₈ reverse phase HPLC column. Various peptide sequences from these two toxins showed similarity to those of other PLA₂ toxins from viperid snake venoms. ACP-TX-I belongs to the catalytically inactive K49 PLA₂ class, while ACP-TX-II is a D49 PLA₂, and is enzymatically active. ACP-TX-I PLA₂ is monomeric, which results in markedly diminished myotoxic and inflammatory activities when compared with dimeric K49 PLA₂s, confirming the hypothesis that dimeric structure contributes heavily to the profound myotoxicity of the most active viperid K49 PLA₂s. ACP-TX-II exhibits the main pharmacological actions reported for this protein family, including in vivo local myotoxicity, edema-forming activity, and in vitro cytotoxicity. ACP-TX-I PLA₂ is cytotoxic to A549 lung carcinoma cells, indicating that cytotoxicity to these tumor cells does not require enzymatic activity.

Enhanced expression of cysteine-rich antimicrobial peptide snakin-1 in Escherichia coli using an aggregation-prone protein coexpression system

Snakin-1 (SN-1) is a cysteine-rich plant antimicrobial peptide and the first purified member of the snakin family. SN-1 shows potent activity against a wide range of microorganisms, and thus has great biotechnological potential as an antimicrobial agent. Here, we produced recombinant SN-1 in Escherichia coli by a previously developed coexpression method using an aggregation-prone partner protein. Our goal was to increase the productivity of SN-1 via the enhanced formation of insoluble inclusion bodies in E. coli cells. The yield of SN-1 by the coexpression method was better than that by direct expression in E. coli cells. After refolding and purification, we obtained several milligrams of functionally active SN-1, the identity of which was verified by MALDI-TOF MS and NMR studies. The purified recombinant SN-1 showed effective antimicrobial activity against test organisms. Our studies indicate that the coexpression method using an aggregation-prone partner protein can serve as a suitable expression system for the efficient production of functionally active SN-1. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1520-1528, 2017.

Production of synthetically created phospholipase A(2) variants with industrial impact

Phospholipases A(2) (PLA(2)) play an important role for the production of lysophospholipids. Presently they are mainly obtained from porcine or bovine pancreas but these mammalian sources are not accepted in several fields of application. To make accessible a non-mammalian PLA(2) to industrial application, synthetic genes encoding PLA(2) from honey bee (Apis mellifera) with modified N-termini were constructed and expressed in Escherichia coli. While expression of the gene with an N-terminal leader sequence to direct the protein into the periplasm failed, four variants with slightly modified N-termini (I1A-PLA(2), I1V-PLA(2), His(6)-tagged PLA(2) and PLA(2) still containing the start methionine) were successfully expressed. In all cases, the PLA(2) variants were produced as inclusion bodies. Their protein content amounted to 26-35% of total cell protein. The optimized renaturation procedure and subsequent purification by cation-exchange chromatography yielded pure active enzymes in yields of 4-11 mg L(-1). The recombinant PLA(2) variants showed activities, far-UV CD and fluorescence spectra similar to the glycosylated PLA(2) isolated from the venom glands of honey bee (bv-PLA(2)). The thermodynamic stabilities of the recombinant enzymes calculated from the transition curves of guanidine hydrochloride induced unfolding were also nearly identical to the stability of bv-PLA(2). For the variant I1A-PLA(2) high-cell density fermentation in 10 L-scale using mineral salt medium was shown to increase the volumetric enzyme yield considerably.

Structural engineering of pMHC reagents for T cell vaccines and diagnostics

MHC class I peptide complexes (pMHC) are routinely used to enumerate T cell populations and are currently being evaluated as vaccines to tumors and specific pathogens. Herein, we describe the structures of three generations of single-chain pMHC progressively designed for the optimal presentation of covalently associated epitopes. Our ultimate design employs a versatile disulfide trap between an invariant MHC residue and a short C-terminal peptide extension. This general strategy is nondisruptive of native pMHC conformation and T cell receptor engagement. Indeed, cell-surface-expressed MHC complexes with disulfide-trapped epitopes are refractory to peptide exchange, suggesting they will make safe and effective vaccines. Furthermore, we find that disulfide-trap stabilized, recombinant pMHC reagents reliably detect polyclonal CD8 T cell populations as proficiently as conventional reagents and are thus well suited to monitor or modulate immune responses during pathogenesis.

Studies on recombinant single chain Jacalin lectin reveal reduced affinity for saccharides despite normal folding like native Jacalin

Sugar binding studies, inactivation, unfolding, and refolding of native Jacalin (nJacalin) from Artocarpus integrifolia and recombinant single-chain Jacalin (rJacalin) expressed in Escherichia coli were studied by intrinsic fluorescence and thermal and chemical denaturation approaches. Interestingly, rJacalin does not undergo any proteolytic processing in an E. coli environment. It has 100fold less affinity for methyl-alpha-galactose (Ka: 2.48 x 10(2)) in comparison to nJacalin (Ka: 1.58 x 10(4)), and it also binds Thomsen-Friedenreich (TF) disaccharide (Galbeta1-3GalNAc) with less affinity. Overall sugar binding characteristics of rJacalin are qualitatively similar to that of nJacalin (Gal<MealphaGal<MealphaTFdisaccharide). Circular dichroism studies at near- and far-UV, thermal, and chemical denaturation studies reveal that the rJacalin behaves like nJacalin. Guanidine hydrochloride-induced denaturation, followed by renaturation, yielded total recovery of sugar binding activity of rJacalin in comparison to partial recovery for nJacalin. This signifies the minor changes in the refolding pathways between native and recombinant lectins. The stability of rJacalin is dramatically reduced in the extreme pH range unlike nJacalin. Both lectins do not bind 1-anilino-8-naphthalene sulfonic acid (ANS) in the pH range of 5 to 12 but they do in the pH range of 1-3. Solute quenching studies of the lectin using acrylamide, KI, and CsCl indicated that the tryptophan residues have full accessibility to the neutral quencher and poor accessibility to ionic quenchers. In summary, biophysical and biochemical studies on the native versus recombinant Jacalin suggest that post-translational modification, i.e., the processing of Jacalin into two chains is probably not a prerequisite for sugar binding but may be required for higher affinity.

Determination of the complete cDNA sequence, construction of expression systems, and elucidation of fibrinolytic activity for Tapes japonica lysozyme

The lysozyme of the marine bivalve, Tapes japonica (13.8 kDa), belongs to the invertebrate lysozyme family and displays both chitinase and isopeptidase activities. We determined the complete cDNA sequence and constructed effective expression systems for this enzyme using Escherichia coli (BL21) and Pichia pastoris. The native and recombinant proteins indicated lysozyme activity and isopeptidase activity, including the proteolysis of d-dimer, a plasminolytic product of stabilized polymeric fibrin. These results will be utilized for the structural and functional study of invertebrate lysozymes, and for the development of applications for thrombosis therapies.

Mapping structural determinants of biological activities in snake venom phospholipases A2 by sequence analysis and site directed mutagenesis

In addition to their catalytic activity, snake venom phospholipases A2 (vPLA2) present remarkable diversity in their biological effects. Sequence alignment analyses of functionally related PLA2 are frequently used to predict the structural determinants of these effects, and the predictions are subsequently evaluated by site directed mutagenesis experiments and functional assays. In order to improve the predictive potential of computer-based analysis, a simple method for scanning amino acid variation analysis (SAVANA) has been developed and included in the analysis of the lysine 49 PLA2 myotoxins (Lys49-PLA2). The SAVANA analysis identified positions in the C-terminal loop region of the protein, which were not identified using previously available sequence analysis tools. Site directed mutagenesis experiments of bothropstoxin-I, a Lys49-PLA2 isolated from the venom of Bothrops jararacussu, reveals that these residues are exactly those involved in the determination of myotoxic and membrane damaging activities. The SAVANA method has been used to analyse presynaptic neurotoxic and anti-coagulant vPLA2s, and the predicted structural determinants of these activities are in excellent agreement with the available results of site directed mutagenesis experiments. The positions of residues involved in the myotoxic and neurotoxic determinants demonstrate significant overlap, suggesting that the multiple biological effects observed in many snake vPLA2s are a consequence of superposed structural determinants on the protein surface.

Crystal structure of an ADP-dependent glucokinase from Pyrococcus furiosus: implications for a sugar-induced conformational change in ADP-dependent kinase

ADP-dependent kinases are used in the modified Embden-Meyerhoff pathway of certain archaea. Our previous study has revealed a mechanism for ADP-dependent phosphoryl transfer by Thermococcus litoralis glucokinase (tlGK), and its evolutionary relationship with ATP-dependent ribokinases and adenosine kinases (PFKB carbohydrate kinase family members). Here, we report the crystal structure of glucokinase from Pyrococcus furiosus (pfGK) in a closed conformation complexed with glucose and AMP at 1.9A resolution. In comparison with the tlGK structure, the pfGK structure shows significant conformational changes in the small domain and a region around the hinge, suggesting glucose-induced domain closing. A part of the large domain next to the hinge is also shifted accompanied with domain closing. In the pfGK structure, glucose binds in a groove between the large and small domains, and the electron density of O1 atoms for both the alpha and beta-anomer configurations was observed. The structural details of the sugar-binding site of ADP-dependent glucokinase were firstly clarified and then site-directed mutagenesis analysis clarified the catalytic residues for ADP-dependent kinase, such as Arg205 and Asp451 of tlGK. Homology search and multiple alignment of amino acid sequences using the information obtained from the structures reveals that eucaryotic hypothetical proteins homologous to ADP-dependent kinases retain the residues for the recognition of a glucose substrate.

Engineering the disulphide bond patterns of secretory phospholipases A2 into porcine pancreatic isozyme. The effects on folding, stability and enzymatic properties

Secretory phospholipases A2 (PLA2s) are small homologous proteins rich in disulphide bridges. These PLA2s have been classified into several groups based on the disulphide bond patterns found [Dennis, E. A. (1997) Trends Biochem. Sci. 22, 1-2]. To probe the effect of the various disulphide bond patterns on folding, stability and enzymatic properties, analogues of the secretory PLA2s were produced by protein engineering of porcine pancreatic PLA2. Refolding experiments indicate that small structural variations play an important role in the folding of newly made PLA2 analogues. Introduction of a C-terminal extension together with disulphide bridge 50-131 gives rise to an enzyme that displays full enzymatic activity having increased conformational stability. In contrast, introduction of a small insertion between positions 88 and 89 together with disulphide bridge 86-89 decreases the catalytic activity significantly, but does not change the stability. Both disulphide bridges 11-77 and 61-91 are important for the kinetic properties and stability of the enzyme. Disulphide bridge 11-77, but not 61-91, was found to be essential to resist tryptic breakdown of native porcine pancreatic PLA2.

Lysine 49 phospholipase A2 proteins

The structures of several K49 PLA2 proteins have been determined and these differ as a group in several regions from the closely related D49 PLA2 enzymes. One outstanding difference is the presence of a high number of positively charged residues in the C-terminal region which combined with the overall high number of conserved lysine residues gives the molecule an interfacial adsorption surface which is highly positively charged compared to the opposite surface of the molecule. Although some nucleotide sequences have been reported, progress in obtaining active recombinant proteins has been slow. The K49 proteins exert several toxic activities, including myotoxicity, anticoagulation and edema formation. The most studied of these activities is myotoxicity. The myotoxicity induced by the K49 PLA2 proteins is histologically similar to that caused by the D49 PLA2 myotoxins, with some muscle fiber types possibly more sensitive than others. Whereas it is clear that the K49 PLA2 myotoxins lyse the plasma membrane of the affected muscle cell in vivo, the exact mechanism of this lysis is not known. Also, it is not known whether the toxin is internalized before, during or after the initial lysis or ever. The K49 PLA2 toxins lyse liposomes and cells in culture and in the latter, the PLA2 myotoxins exert at least two distinct mechanisms of action, neither of which is well-characterized. While the K49 PLA2 proteins are enzymatically inactive on artificial substrates, the toxins cause fatty acid production in cell cultures. Whether the fatty acid release is due to the enzymatic activity of the K49 PLA2 or stimulation of tissue lipases, is unknown. While there may be a role for fatty acid production in one mechanism of myotoxicity, a second mechanism appears to be independent of enzymatic activity. Although we are beginning to understand more about the structure of these toxins, we still know little about the precise mechanism by which they interact with the skeletal muscle cell in vivo.

Diversity of cDNAs encoding phospholipase A2 from Agkistrodon halys pallas venom, and its expression in E. coli

As a step toward understanding the structure and function of phospholipase A2(PLA2), we isolated several novel cDNAs encoding Agkistrodon halys Pallas PLA2 isoenzymes including B-PLA2, Asn49-PLA2, A-PLA2, A'-PLA2 and BA1-PLA2 by polymerase chain reaction with oligonucleotide primers corresponding to the N- and C-terminus of these enzymes. The amino acid sequences of A-PLA2 deduced from cDNA are consistent with that isolated from venom except for four residues. Asn49-PLA2 and B-PLA2 are highly similar (> 95%), but the critical residue Asp49 in the active centre of B-PLA2 is replaced by Asn49 in Asn49-PLA2. The N-terminal residues (1-24) of BA1-PLA2 shows high similarity to that of B-PLA2 which has strong ability to hemolyze erythrocytes, while its C-terminal residues (72-125) are the same as that of A-PLA2 which can inhibit platelet aggregation. The successful cloning of these isoenzymes not only provide excellent native material to study the structure-function relationship of PLA2s, but also to disclose the genesis of structural diversity of PLA2s, namely DNA modification and gene rearrangement. The cloned cDNA for A-PLA2 has been expressed in E. coli. By Q-Sepharose column chromatography, denaturation-renaturation and FPLC, we obtained the active recombinant protein with the initiator Met. This is the first report of the production of an active recombinant PLA2 with the initiator Met.

Expression and secondary structure determination by NMR methods of the major house dust mite allergen Der p 2

There exists a strong correlation between asthma and sensitization to indoor allergens. This study reports on the secondary structure of the major house dust mite allergen Der p 2, determined using heteronuclear NMR methods. The DNA was subcloned from the yeast expression vector pSAY1 into the high yield bacterial expression vector pET21a, resulting in yields of 50 mg/liter. The recombinant protein was shown to have immunoreactivity comparable with that of the natural mite protein using competitive inhibition enzyme-linked immunosorbent assay (ELISA) and a modified monoclonal radioallergosorbent test (RAST). The secondary structure was determined by examining chemical shifts, short and long range NOESYs, JHN-HA coupling constants, and amide exchange rates. From these data, it is clear that Der p 2 is composed of beta-sheets and random coil. Based on long range distance constraints, a number of beta-strands were aligned into two three-stranded, anti-parallel beta-sheets.

The role of the amino terminus in the kinetics and assembly of alpha-hemolysin of Staphylococcus aureus

The nature of the involvement of an intact NH2 terminus in the assembly of alpha-hemolysin of Staphylococcus aureus was reinvestigated. For the first time, a deletion of the first four amino acids at the NH2 terminus of alpha-hemolysin yielded a novel mutant that undergoes all of the conformational changes to form a lytic pore. The experimental evidence shows unequivocally that the mutant toxin forms heat- and sodium dodecyl sulfate-stable heptameric oligomers. The concentration required to achieve 50% lysis of red blood cells is around 58-116 ng/ml, and the time taken to achieve lysis to the same extent as that of intact toxin is considerably longer. Transmission electron microscopic studies also suggest that the pores formed by this deletion mutant are similar to those by the full-length toxin. This is in contrast to the previously reported 2- and 11-amino acid deletions that failed to proceed further from a presumed prefinal nonlytic pore to a lytic pore. Studies on the kinetics of assembly indicate that this mutant can form heat- and sodium dodecyl sulfate-stable oligomers as fast as full-length alpha-hemolysin but that pore opening is slowed down. The data strongly suggest that these amino acids (Ala-Asp-Ser-Asp) are involved in the final stages of assembly of alpha-hemolysin in target membranes.

Availability of a second upstream AUG can completely overcome inhibition of protein synthesis initiation engendered by mRNA secondary structure encompassing the start codon

Secondary structure analysis of the mRNA from a nonproductive construct carrying the nonstructural gene 3 (NS3) of Japanese Encephalitis Virus revealed the presence of a potential 28 nucleotide long stem and loop beginning with the guanine of the initiation codon AUG that had a calculated stabilization energy of -13 kcal/mol (delta Gfzero). Provision of an additional AUG along with three codons upstream resulted in complete relief of inhibition. N-terminal amino acid sequence of the recombinant protein was consistent with initiation of protein synthesis having occurred from the upstream AUG. Similar levels of NS3 specific RNA in E. coli cells carrying the expressing and nonexpressing constructs and restoration of recombinant protein expression following deletion of segments beginning with the stem and loop confirmed the role of this structure in blocking expression at the level of translation initiation. Our approach exploits the ability of a ribosome in motion to open up downstream secondary structural elements of considerable stability and represents a novel and widely applicable strategy to overcome a block in translation initiation caused by mRNA secondary structure around the translation start site.

Regulation of sCD4-183 gene expression from phage-T7-based vectors in Escherichia coli

In this paper, we describe various parameters affecting the regulation of expression of the sCD4-183 gene, encoding the 183-amino-acid soluble human two-domain CD4 protein, from phage-T7-based pET vectors. We demonstrated that for the sCD4-183 protein, the highest protein yield was obtained using vector pET-9a, in which neither expression of the T7 RNA polymerase-encoding gene nor the target gene was tightly regulated. The highest overall protein yield was obtained from cells grown for 24 h in the absence of inducer, a strategy that may be generally useful for production of less toxic proteins. We also describe two modifications of the pET vector system that effectively minimized leaky (uninduced) expression and enhanced plasmid stability. These have potential use in the production of toxic proteins, or of non-toxic proteins produced in high-density cultures.

Quantification of the interaction between lysolecithin and phospholipase A2

The rate of hydrolysis of phosphatidylcholine bilayers by phospholipase A2 may be either enhanced or inhibited by the presence of lysolecithin depending on the experimental conditions examined. To further understand the relationship of lysolecithin to phospholipase A2 activity, the binding of lysolecithin to phospholipase A2 from the venom of Agkistrodon piscivorus piscivorus was examined by fluorescence spectroscopy. The tryptophan emission intensity of the enzyme was enhanced by 70% upon addition of lysolecithin. The binding isotherm for lysolecithin to the phospholipase A2 estimated from the fluorescence change was biphasic, with a clear break in the curve occurring at the critical micelle concentration of the lysolecithin. Several observations suggested that the phospholipase A2 was capable of hydrolyzing the lysolecithin although at a rate far below that of phospholipid hydrolysis. These experiments were repeated using several other species of phospholipase A2, and the results were found to be general among the enzymes except the lys-49 isozyme from A. p. piscivorus which displayed neither the dependence on the critical micelle concentration for binding nor the ability to hydrolyze lysolecithin. These results were used as the basis for a quantitative analysis of enzyme fluorescence changes that occur during the time course of phospholipid hydrolysis and of the mechanism whereby lysolecithin inhibits the hydrolysis of phosphatidylcholine bilayers by phospholipase A2.

Expression of fully active ammodytoxin A, a potent presynaptically neurotoxic phospholipase A2, in Escherichia coli

A cDNA encoding the most presynaptically neurotoxic phospholipase A2, ammodytoxin A, from the venom of the long-nosed viper (Vipera ammodytes ammodytes) has been expressed in Escherichia coli. Ammodytoxin A was produced as a fusion protein with the 81 N-terminal residues of adenylate kinase followed by the tetrapeptide recognition site for factor Xa (IEGR) just preceding the first amino acid residue of the toxin. The fusion protein was expressed under the control of tac promoter without IPTG induction in the form of insoluble inclusion bodies. It was dissolved in guanidine hydrochloride, S-sulfonated and refolded in a reoxidation mixture including a reduced/oxidized glutathione redox couple. Ammodytoxin A was fully activated by limited hydrolysis with trypsin that preferentially cleaves the fusion protein at the factor Xa recognition site and purified by cation-exchange chromatography. The correct N-terminus was confirmed by protein sequencing. Recombinant ammodytoxin A has been proved to be indistinguishable from the native toxin in its enzymatic activity and toxicity.