响应面法优化提取虎耳草总酚及其抑制五步蛇毒PLA2酶活性的相关性

为了探讨虎耳草总酚（TP）与抑制五步蛇毒中磷脂酶A₂（PLA₂）之间的关系,本研究通过单因素试验及Box-Behnken试验对虎耳草TP的提取条件与抑制五步蛇毒中PLA₂活性进行优化,考察各试验因素对超声辅助提取虎耳草TP得率及其对五步蛇毒PLA₂活性抑制率（PIR）的作用,并对虎耳草TP含量与PIR的相关性进行分析。结果表明,响应面法提取虎耳草TP和PIR的最佳工艺条件为：粒径为60目,料液比为1∶50,超声功率为250 W,超声时间为1.8 h。此优化工艺条件下虎耳草TP得率为（8.69±0.46） mg·g^-1,PIR为（40.91±0.21）%;相关性分析结果显示虎耳草TP含量与PIR具有极显著正相关（P<0.01）,说明TP可能为虎耳草抑制五步蛇毒中PLA₂活性的物质基础。     

Solution structure of P01, a natural scorpion peptide structurally analogous to scorpion toxins specific for apamin-sensitive potassium channel

The venom of the North African scorpion Androctonus mauretanicus mauretanicus possesses numerous highly active neurotoxins that specifically bind to various ion channels. One of these, P05, has been found to bind specifically to calcium-activated potassium channels and also to compete with apamin, a toxin extracted from bee venom. Besides the highly potent ones, several of these peptides (including that of P01) have been purified and been found to possess only a very weak, although significant, activity in competition with apamin. The amino acid sequence of P01 shows that it is shorter than P05 by two residues. This deletion occurs within an α-helix stretch (residues 5–12). This α-helix has been shown to be involved in the interaction of P05 with its receptor via two arginine residues. These two arginines are absent in the P01 sequence. Furthermore, a proline residue in position 7 of the P01 sequence may act as an α-helix breaker. We have determined the solution structure of P01 by conventional two-dimensional ¹H nuclear magnetic resonance and show that 1) the proline residue does not disturb the α-helix running from residues 5 to 12; 2) the two arginines are topologically replaced by two acidic residues, which explains the drop in activity; 3) the residual binding activity may be due to the histidine residue in position 9; and 4) the overall secondary structure is conserved, i.e., an α-helix running from residues 5 to 12, two antiparallel stretches of β-sheet (residues 15–20 and 23–27) connected by a type I′ β-turn, and three disulfide bridges connecting the α-helix to the β-sheet.     

Sulfated sialic acid-polymers inhibit the cytotoxic action of bee and snake venom

Colominic acid is an 2,8-linked sialic acid polymer produced by Escherichia coli. We found that synthetic sulfated-colominic acids (SC) remarkably inhibited the cytotoxicity of bee and snake venom toward mouse fibroblast cells, but colominic acids showed no inhibition themselves, indicating the important role of sulfate groups in the inhibitory activity of SC. Other sulfated carbohydrates such as chondroitin sulfates, heparin and heparan sulfate showed no inhibition. SC also exhibited potent inhibition of melittin, a highly basic peptide, which is a major cytotoxic component of bee venom. SC did not inhibit phospholipase A₂ activity in bee venom. This suggests that the inhibition of bee and snake venom by SC is due to inhibition of melittin and cardiotoxin, which is a cytolytic peptide in snake venom, respectively. SC with a higher sulfur content and a larger molecular mass showed more potent activity. The interaction between SC and melittin basically seems an ionic one, however, the conformation of SC is also likely important. For the binding of SC to melittin leading loss of its cytotoxic activity, the sulfate groups of SC must be properly arranged to interact with lysine and arginine residues of melittin molecules, which play an important role in the cytolytic activity. A higher molecular mass of SC substituted with more sulfate groups is required for more obvious inhibition of the cytotoxic activity.     

Structural and functional characterization of N-terminally blocked peptides isolated from the venom of the social wasp Polybia paulista

Two novel peptides were isolated from the crude venom of the social wasp Polybia paulista, by using RP-HPLC under a gradient of MeCN from 5 to 60% (v/v) and named Polybine-I and -II. Further purification of these peptides under normal phase chromatography, rendered pure enough preparations to be sequenced by Edman degradation chemistry. However, both peptides did not interact with phenylisothiocyanate reagent, suggesting the existence of a chemically blocked N-terminus. Therefore, the sequences of both peptides were assigned by ESI-MS/MS under CID conditions, as follows: Polybine-I Ac-SADLVKKIWDNPAL-NH₂ (Mr 1610 Da) and Polybine-II Ac-SVDMVMKGLKIWPL-NH₂ (Mr 1657 Da). During the tandem mass spectrometry experiments, a loss of 43 a.m.u. was observed from the N-terminal residue of each peptide, suggesting the acetylation of the N-terminus. Subsequently, the peptides with and without acetylation were synthesized on solid phase and submitted to functional characterizations; the biological activities investigated were: hemolysis, chemotaxis of polymorphonucleated leukocytes (PMNL), mast cell degranulation and antibiosis. The results revealed that the acetylated peptides exhibited more pronounced chemotaxis of PMNL cells and mast cell degranulation than the respective non-acetylated congeners; no hemolytic and antibiotic activities were observed, irrespective to the blockage or not of the -amino groups of the N-terminal residues of each peptide. Therefore, the N-terminal acetylation may be related to the increase of the inflammatory activity of both peptides.     

On the modeling of snake venom serine proteinase interactions with benzamidine-based thrombin inhibitors

Pit viper venoms contain a number of serine proteinases that exhibit one or more thrombin-like activities on fibrinogen and platelets, this being the case for the kinin-releasing and fibrinogen-clotting KN-BJ from the venom of Bothrops jararaca. A three-dimensional structural model of the KN-BJ2 serine proteinase was built by homology modeling using the snake venom plasminogen activator TSV-PA as a major template and porcine kallikrein as additional structural support. A set of intrinsic buried waters was included in the model and its behavior under dynamic conditions was molecular dynamics simulated, revealing a most interesting similarity pattern to kallikrein. The benzamidine-based thrombin inhibitors alpha-NAPAP, 3-TAPAP, and 4-TAPAP were docked into the refined model, allowing for a more insightful functional characterization of the enzyme and a better understanding of the reported comparatively low affinity of KN-BJ2 toward those inhibitors.     

Allosteric interactions among pyrethroid,brevetoxin, and scorpion toxin receptors on insect sodium channels raise an alternative approach for insect control

Intensive pyrethroid use in insect control has led to resistance buildup among various pests. One alternative to battle this problem envisions the combined use of synergistically acting insecticidal compounds. Pyrethroids, scorpion - and β-toxins, and brevetoxins bind to distinct receptor sites on voltage-gated sodium channels (NaChs) and modify their function. The binding affinity of scorpion -toxins to locust, but not rat-brain NaChs, is allosterically increased by pyrethroids and by brevetoxin-1. Brevetoxin-1 also increases the binding of an excitatory β-toxin to insect NaChs. These results reveal differences between insect and mammalian NaChs and may be exploited in new strategies of insect control.     

The water-soluble fraction of bee venom produces antinociceptive and anti-inflammatory effects on rheumatoid arthritis in rats

We recently demonstrated that bee venom (BV) injection into the Zusanli acupoint produced a significantly more potent anti-inflammatory and antinociceptive effect than injection into a non-acupoint in a Freund's adjuvant induced rheumatoid arthritis (RA) model. However, the precise BV constituents responsible for these antinociceptive and/or anti-inflammatory effects are not fully understood. In order to investigate the possible role of the soluble fraction of BV in producing the anti-arthritic actions of BV acupuncture, whole BV was extracted into two fractions according to solubility (a water soluble fraction, BVA and an ethylacetate soluble fraction, BVE) and the BVA fraction was further tested.Subcutaneous BVA injection (0.9 mg/kg/day) into the Zusanli acupoint was found to dramatically inhibit paw edema and radiological change (i.e. new bone proliferation and soft tissue swelling) caused by Freund's adjuvant injection. BVA treatment also reduced the increase in serum interleukin-6 caused by RA induction to levels observed in non-arthritic animals. In addition, BVA therapy significantly reduced arthritis-induced nociceptive behaviors (i.e. nociceptive scores for mechanical hyperalgesia and thermal hyperalgesia). Finally, BVA treatment significantly suppressed adjuvant-induced Fos expression in the lumbar spinal cord at 3 weeks post-adjuvant injection. In contrast, BVE treatment (0.05 mg/kg/day) failed to show any anti-inflammatory or antinociceptive effects on RA.The results of the present study demonstrate that BVA is the effective fraction of whole BV responsible for the antinociception and anti-inflammatory effects of BV acupuncture treatment. Thus it is recommended that this fraction of BV be used for long-term treatment of RA-induced pain and inflammation. However, further study is necessary to clarify which constituents of the BVA fraction are directly responsible for these anti-arthritis effects.     

Separation and purification of Echis coloratus venom and some biological and biochemical effects of the proteins

Crude venom of Echis coloratus was separated into seven protein fractions using 7% preparative native polyacrylamide gel electrophoresis. The effect of crude venom and seven venom protein fractions (F1-F7) from Echis coloratus on key metabolic activities of fibroblast cultures was investigated. Confluent cultures were incubated with the venom proteins for 3 h at 37 degrees C. The specific activity of phosphofructokinase, was significantly lowered upon incubation with the crude venom and with fractions 2, 3, 4 and 6. Citrate synthase activity was significantly lowered by the crude venom and by fractions 2 and 3. Glycogen phosphorylase activity was significantly increased by the crude venom and by fractions 2, 3, 4 and 6 leading to a significant concurrent drop in glycogen content. Creatine kinase activity was significantly increased by the crude venom and by fractions 3, 4, 5 and 6. Cellular ATP levels rose significantly upon incubation with the crude venom and with fractions 3, 4, 5 and 6. Incubation of cell sonicates with all the venom proteins did not significantly alter the activity or content of any of the studied parameters.     

A novel short neurotoxin,cobrotoxin c,from monocellate cobra (Naja kaouthia) venom: isolation and purification,primary and secondary structure determination,and tertiary structure modeling

A novel short neurotoxin, cobrotoxin c (CBT C) was isolated from the venom of monocellate cobra (Naja kaouthia) using a combination of ion-exchange chromatography and FPLC. Its primary structure was determined by Edman degradation. CBT C is composed of 61 amino acid residues. It differs from cobrotoxin b (CBT B) by only two amino acid substitutions, Thr/Ala11 and Arg/Thr56, which are not located on the functionally important regions by sequence similarity. However, the LD50 is 0.08 mg/g to mice, i.e. approximately five-fold higher than for CBT B. Strikingly, a structure-function relationship analysis suggests the existence of a functionally important domain on the outside of Loop III of CBT C. The functionally important basic residues on the outside of Loop III might have a pairwise interaction with alpha subunit, instead of gamma or delta subunits of the nicotinic acetylcholine receptor (nAChR).     

Two new scorpion toxins that target voltage-gated Ca2+ and Na+ channels

This report describes the isolation, primary structure determination, and functional characterization of two similar toxins from the scorpion Parabuthus granulatus named kurtoxin-like I and II (KLI and KLII, respectively). KLII from P. granulatus is identical to kurtoxin from Parabuthus transvaalicus (a 63 amino-acid long toxin) whereas KLI is a new peptide containing 62 amino acid residues closely packed by four disulfide bridges with a molecular mass of 7244. Functional assays showed that both toxins, KLI and kurtoxin from P. granulatus, potently inhibit native voltage-gated T-type Ca(2+) channel activity in mouse male germ cells. In addition, KLI was shown to significantly affect the gating mechanisms of recombinant Na(+) channels and weakly block alpha(1)3.3Ca(V) channels expressed in Xenopus oocytes. KLI and kurtoxin from P. granulatus represent new probes to study the role of ion channels in germ cells, as well as in cardiac and neural tissue.