Purification, characterization and binding interactions of the Chinese-cobra (Naja naja atra) serum antitoxic protein CSAP

Proteomic Investigations of Two Pakistani Naja Snake Venoms Species Unravel the Venom Complexity, Posttranslational Modifications, and Presence of Extracellular Vesicles

Latest advancement of omics technologies allows in-depth characterization of venom compositions. In the present work we present a proteomic study of two snake venoms of the genus Naja i.e., Naja naja (black cobra) and Naja oxiana (brown cobra) of Pakistani origin. The present study has shown that these snake venoms consist of a highly diversified proteome. Furthermore, the data also revealed variation among closely related species. High throughput mass spectrometric analysis of the venom proteome allowed to identify for the N. naja venom 34 protein families and for the N. oxiana 24 protein families. The comparative evaluation of the two venoms showed that N. naja consists of a more complex venom proteome than N. oxiana venom. Analysis also showed N-terminal acetylation (N-ace) of a few proteins in both venoms. To the best of our knowledge, this is the first study revealing this posttranslational modification in snake venom. N-ace can shed light on the mechanism of regulation of venom proteins inside the venom gland. Furthermore, our data showed the presence of other body proteins, e.g., ankyrin repeats, leucine repeats, zinc finger, cobra serum albumin, transferrin, insulin, deoxyribonuclease-2-alpha, and other regulatory proteins in these venoms. Interestingly, our data identified Ras-GTpase type of proteins, which indicate the presence of extracellular vesicles in the venom. The data can support the production of distinct and specific anti-venoms and also allow a better understanding of the envenomation and mechanism of distribution of toxins. Data are available via ProteomeXchange with identifier PXD018726.

Purification and physico-chemical study of serum albumins of two neotropical fish species from the São Francisco River Bassin, Brazil

This paper presents results from a study of albumin from pacu (Piaractus mesopotamicus, Holmberg 1887) and the catfish pintado (Pseudoplatystoma corruscans, Spix & Agassiz, 1829), two neotropical fish species inhabitants of Brazilian rivers, comparing their molecular mass and discussing their secondary structures based on spectropolarimetric (circular dychroism) measurements. Genetic controlled specimens were obtained from two fish hatcheries, located in Mococa (pacu) and in São João da Boa Vista (pintado), both in São Paulo State, Brazil. After a period of adaptation in holding tanks, fish blood samples were taken by punctioning their abdominal aorta. Purified albumin was obtained by gel filtration. SDS-PAGE electrophoresis was performed for the molecular mass estimation. Circular Dichroism spectra were registered for albumins of the two fish species over the range of 190-250 nm (far-UV), which shown two negative bands at 217 and 208 nm, a positive peak at 196 nm and a crossover at 200 nm. This profile is compatible with proteins that content predominantly alpha-helix structure.

Proteomic characterization of venom of the medically important Southeast Asian Naja sumatrana (Equatorial spitting cobra)

The proteome of Naja sumatrana (Equatorial spitting cobra) venom was investigated by shotgun analysis and a combination of ion-exchange chromatography and reverse phase HPLC. Shotgun analysis revealed the presence of 39 proteins in the venom while the chromatographic approach identified 37 venom proteins. The results indicated that, like other Asiatic cobra venoms, N. sumatrana contains large number of three finger toxins and phospholipases A2, which together constitute 92.1% by weight of venom protein. However, only eight of the toxins can be considered as major venom toxins. These include two phospholipases A2, three neurotoxins (two long neurotoxins and a short neurotoxin) and three cardiotoxins. The eight major toxins have relative abundance of 1.6-27.2% venom proteins and together account for 89.8% (by weight) of total venom protein. Other venom proteins identified include Zn-metalloproteinase-disintegrin, Thaicobrin, CRISP, natriuretic peptide, complement depleting factors, cobra venom factors, venom nerve growth factor and cobra serum albumin. The proteome of N. sumatrana venom is similar to proteome of other Asiatic cobra venoms but differs from that of African spitting cobra venom. Our results confirm that the main toxic action of N. sumatrana venom is neurotoxic but the large amount of cardiotoxins and phospholipases A2 are likely to contribute significantly to the overall pathophysiological action of the venom. The differences in toxin distribution between N. sumatrana venom and African spitting cobra venoms suggest possible differences in the pathophysiological actions of N. sumatrana venom and the African spitting cobra venoms, and explain why antivenom raised against Asiatic cobra venom is not effective against African spitting cobra venoms.

Proteomic Analysis of the Ontogenetic Variability in Plasma Composition of Juvenile and Adult Bothrops jararaca Snakes

The ontogenetic variability in venom composition of some snake genera, including Bothrops, as well as the biological implications of such variability and the search of new molecules that can neutralize the toxic components of these venoms have been the subject of many studies. Thus, considering the resistance of Bothrops jararaca to the toxic action of its own venom and the ontogenetic variability in venom composition described in this species, a comparative study of the plasma composition of juvenile and adult B. jararaca snakes was performed through a proteomic approach based on 2D electrophoresis and mass spectrometry, which allowed the identification of proteins that might be present at different levels during ontogenetic development. Among the proteins identified by mass spectrometry, antihemorrhagic factor Bj46a was found only in adult plasma. Moreover, two spots identified as phospholipase A₂ inhibitors were significantly increased in juvenile plasma, which can be related to the higher catalytic PLA₂ activity shown by juvenile venom in comparison to that of adult snakes. This work shows the ontogenetic variability of B. jararaca plasma, and that these changes can be related to the ontogenetic variability described in its venom.

Purification and characterization of antitoxic proteins from the serum of Agkistrodon halys Pallas

In this study, the authors report the purification and characterization of antitoxic proteins from the serum of Agkistrodon halys Pallas. Two antitoxic proteins have been successfully isolated by the methods of (NH4)(2)SO(4) fractional precipitation, chromatography and preparative discontinuous polyacrylamide gel electrophoresis (PAGE). We have measured their molecular weights by Sephadex G-150 chromatography and 0.1% SDS-Tris-HCl discontinue PAGE respectively. Antitoxin I was about 138,000+/-40 Da and antitoxin II was about 76,000+/-40 Da, they are all single-chain peptides. We have measured their capacity to neutralize the toxicity of agkistrodotoxin (ATX), and their capacity to inhibit the PLA(2) activity of ATX. The results showed that antitoxin I could increase LD(50) of ATX from 0.25+/-0.05 to 0.445+/-0.13 mg/kg, decrease its PLA(2) activity from 2.36 to 1.72 microm/mg min, and antitoxin II could increase LD(50) of ATX from 0.25+/-0.05 to 0.56+/-0.12 mg/kg, decrease Phospholipase A(2) (PLA(2)) activity from 2.36 to 1.2 microm/mg min. When the natural antitoxins were mixed with different amounts of ATX and inoculated intraperitonially into eight mice, it was found that 0.5 mg antitoxin I could neutralize the toxicity of 0.4 mg ATX and 0.5 mg antitoxin II could neutralize the toxicity of 0.5 mg ATX completely. These antitoxic proteins could neutralize the toxicity of ATX completely and inhibit ATX's PLA(2) activity partially.

Interaction of the neurotoxic and nontoxic secretory phospholipases A2 with the crotoxin inhibitor from Crotalus serum

Crotalus durissus terrificus snakes possess a protein in their blood, named crotoxin inhibitor from Crotalus serum (CICS), which protects them against crotoxin, the main toxin of their venom. CICS neutralizes the lethal potency of crotoxin and inhibits its phospholipase A2 (PLA2) activity. The aim of the present study is to investigate the specificity of CICS towards snake venom neurotoxic PLA2s (beta-neurotoxins) and nontoxic mammalian PLA2s. This investigation shows that CICS does not affect the enzymatic activity of pancreatic and nonpancreatic PLA2s, bee venom PLA2 and Elapidae beta-neurotoxins but strongly inhibits the PLA2 activity of Viperidae beta-neurotoxins. Surface plasmon resonance and PAGE studies further demonstrated that CICS makes complexes with monomeric and multimeric Viperidae beta-neurotoxins but does not interact with nontoxic PLA2s. In the case of dimeric beta-neurotoxins from Viperidae venoms (crotoxin, Mojave toxin and CbICbII), which are made by the noncovalent association of a PLA2 with a nonenzymatic subunit, CICS does not react with the noncatalytic subunit, instead it binds tightly to the PLA2 subunit and induces the dissociation of the heterocomplex. In vitro assays performed with Torpedo synaptosomes showed a protective action of CICS against Viperidae beta-neurotoxins but not against other PLA2 neurotoxins, on primary and evoked liberation of acetylcholine. In conclusion, CICS is a specific PLA2 inhibitor of the beta-neurotoxins from the Viperidae family.

Fatty acid binding to human serum albumin: new insights from crystallographic studies

Human serum albumin possesses multiple fatty acid binding sites of varying affinities, but the precise locations of these sites have remained elusive. The determination of the crystal structure of human serum albumin complexed with myristic acid recently revealed the positions and architecture of six binding sites on the protein. While the structure of the complex is consistent with a great deal of the biochemical and biophysical data on fatty acid binding, it is not yet possible to provide a completely rigorous correlation between the structural and binding data. The challenge now is to use the new structural information to design experiments that will identify the physiologically important binding sites on HSA and provide a much richer description of fatty acid interactions with the protein.

Snake envenomation and protective natural endogenous proteins: a mini review of the recent developments (1991-1997)

The properties of several factors--antihaemorrhagic, antineurotoxic, antimyotoxic--isolated from the blood serum or plasma of different animals are described with more emphasis placed on the structural differences and similarities among the factors of the snake (Trimeresurus flavoviridis) and mammals (Didelphis marsupials and Herpestes edwardsii). Classification of antihaemorrhagic factors of snake and mammals according to structural homologies, and their effectiveness in neutralizing venom haemorrhagic activities in comparison with that of commercial antivenoms are also reviewed. The antineurotoxic factors isolated so far from the sera of viperid (Vipera palestinae, Daboia r. siamensis), crotalid (Crotalus d. terrificus, T. flavoviridis, Agkistrodon b. siniticus) and elapid (Naja naja atra) snakes, as reviewed, are inhibitors of phospholipase A2, and the amino acid sequences, particularly of those inhibitors from the sera of crotalid snakes, do not share significant sequence homology even within the same family Crotalidae. The amino acid sequences of antineurotoxic factors of the snake (Crotalus d. terrificus) also are not homologous to those of the antihaemorrhagic factors from the blood of the snake (T. flavoviridis) or mammals (Didelphis virginiana, Herpestes edwardsii). The mechanism of action of antihaemorrhagic and antineurotoxic factors is briefly discussed as well as the possibility that crotalids and viperids might possess both of those endogenous neutralizing factors in their blood. Some recent findings on the antimyotoxic factors from the snake serum or plasma with inhibition properties against PLA2 activity and myotoxicity of venoms or toxins are also shortly reviewed.

Elucidation of a new biological function of an old protein: unique structure of the cobra serum albumin controls its specific toxin binding activity

Although few proteins have been studies as thoroughly as serum albumin, a new biological property of this evolutionary ancient protein was recently discovered: The ability of cobra serum albumin (CSA) to specifically sequester lethal endogenous toxins. A study of the structural basis of this property is reported in this contribution. Two independent approaches were used to alter the structure of the CSA at defined positions: Directed mutagenesis and limited proteolysis. The conserved pattern of the disulfide linkages in the primary structure of the serum albumins showed in the case of the cobra snake (Naja naja kaouthia) an anomaly at C11 and C502, which suggested the existence of a unique spatial structure in this protein. The two cysteine residues were singly replaced with the consensus residue, i.e. C11-->F and C502-->T. The former substitution increased the specific neurotoxin binding capacity of the CSA by the factor 1.7 +/- 0.2, whereas the latter replacement reduced it to (25 +/- 2)%. The limited proteolysis yielded the large tryptic peptides T60, T40, T30 and T18, which after isolation by PAGE followed by HPLC had retained a strong toxin affinity. The location of these peptides in the amino-acid sequence was identified by Edman degradation and suggested the order of their release. On the basis of these data, a model of the unfolding and of the activity changes of the CSA caused by the structural perturbations was composed and the kinetic parameters associated with the process were evaluated. The results support the hypothesis of the existence of a structure of multiple homologous domains with a disulfide linkage between C11 and C502 in the native CSA that joins the chain ends to form a dense conformation.

Purification and partial amino acid sequences of two distinct albumins from turtle plasma

Two putative albumins, denoted Alb-1 (apparent molecular mass of 67 kDa) and Alb-2 (68 kDa), were purified from plasma of the emydid turtle (Trachemys scripta). Concentrations in serum or plasma were determined by radioimmunoassay using 125I-labeled Alb-1. In juvenile turtles (less than 2 years of age), serum concentrations of Alb-1 and Alb-2 were 2.72 +/- 0.23 mg/ml and 1.68 +/- 0.22 mg/ml, respectively, while concentrations in plasma pooled from adult turtles were 4.2 mg/ml and 2.6 mg/ml, respectively. The two albumins are immunologically distinct from one another as determined by both radioimmunoassay with 125I-labeled Alb-1 and Western blot analysis with antichicken albumin antiserum. Determination of the amino acid compositions of Alb-1 and Alb-2, and of albumin purified from plasma of the common snapping turtle (Chelydra serpentina), suggested that Alb-1 is more similar to albumins of other animals than is Alb-2. This was also indicated by Western blot analysis and by determining the N-terminal amino acid sequences of Alb-1 (40 residues) and Alb-2 (15 residues). Thus, it appears that two distinct forms of albumin are synthesized by T. scripta, possibly as a result of gene duplication and divergence.

Isolation, characterization and mode of neutralization of a potent antihemorrhagic factor from the serum of the snake Bothrops asper

A potent antihemorrhagic factor (BaSAH1) was isolated from the serum of the snake Bothrops asper by ammonium sulfate precipitation at 40-60%, Sephacryl S-200 and Sephadex G-50 gel filtration, DEAE-Sepharose, and hydrophobic Phenyl-Sepharose chromatography. The purified protein showed one band with an isoelectric point of 5.2 and a molecular weight of 66 kDa. 4 micrograms of the purified factor BaSAH were needed to neutralize the hemorrhagic dose of B. asper whole venom compared to 60 micrograms of the clinically used horse polyvalent immunoglobulins. Moreover, 0.35 microgram of BaSAH were sufficient to achieve complete neutralization of the main hemorrhagic toxin (BaH1), with a molar ratio of 2:1. The antihemorrhagic activity was stable between pH 1.5-9 and up to 60 degrees C but lost activity completely after 30 min of heating at 70 degrees C. BaSAH did not digest the hemorrhagic toxin BaH1 or formed a precipitin line with it, nor with the whole venom. Both ELISA experiments and chromatography of BaSAH after incubation with the 125I-labeled hemorrhagic toxin BaH1 demonstrated that the mechanism of the neutralization involves a formation of an inactive soluble complex between the natural antihemorrhagin and the main hemorrhagin of B. asper venom.

Molecular structure and mechanism of action of the crotoxin inhibitor from Crotalus durissus terrificus serum

An antivenom protein has been identified in the blood of the snake Crotalus durissus terrificus and proved to act by specifically neutralizing crotoxin, the main lethal component of rattlesnake venoms. The aim of this study was to purify the crotoxin inhibitor from Crotalus serum (CICS), and to analyze its mechanism of action. CICS has been purified from blood serum of the Crotalus snake by gel filtration on Sephadex G-200, ion-exchange chromatography on DEAE-Sephacel, and FPLC gel filtration on a Superose 12 column. It is an oligomeric glycoprotein of 130 kDa, made by the non-covalent association of 23-25-kDa subunits. Two different subunit peptides were identified by SDS/PAGE, however, their N-terminal sequences are identical. They are characterized by the absence of methionine residues and a high content of acidic, hydrophobic and cysteine residues. The neutralizing effect of purified CICS towards the neurotoxic effects of crotoxin has been demonstrated in vivo by lethality assays. CICS binds to the phospholipase subunit CB of crotoxin, but not to the acidic chaperon subunit CA; it efficiently inhibits the phospholipase activity of crotoxin and its isolated CB subunit and evokes the dissociation of the crotoxin complex. The molecular mechanism of the interaction between CICS and crotoxin seems to be very similar to that of crotoxin with its acceptor. It is, therefore, tempting to suggest that CICS acts physiologically as a false crotoxin acceptor that would retain the toxin in the vascular system, thus preventing its action on the neuromuscular system.

A potent antihemorrhagin in the serum of the non-poisonous water snake Natrix tessellata: isolation, characterization and mechanism of neutralization

The main natural antihemorrhagic factor (NtAH), which inhibits the hemorrhagic activity of Bothrops asper snake venom, was isolated from the serum of the non-poisonous water snake Natrix tessellata by ammonium sulfate precipitation at 35-55%, Sephadex G-75 gel filtration, ion exchange chromatography on DEAE-Sepharose and CM-Sepharose and hydrophobic Phenyl-Sepharose chromatography. The purified protein showed one band with an isoelectric point of 4.5 and a molecular mass of about 880 kDa. The antihemorrhagic activity was stable between pH 5.5-11.7 and up to 50 degrees C, but lost activity after 20 min at 60 degrees C. It did not form a precipitin line with the main hemorrhagin of Bothrops asper snake venom (BaH1), nor with the whole venom, which suggests that the antihemorrhagic factor is not an immunoglobulin. The mechanism of neutralization by the isolated antihemorrhagic factor NtAH did not include digestion of the hemorrhagic toxin BaH1. Chromatography of NtAH with active 125I-labeled BaH1 toxin as well as ELISA experiments demonstrated that the mechanism of neutralization involves formation of an inactive soluble complex between the natural NtAH of the non-poisonous water snake and the main hemorrhagin of Bothrops asper venom.