Snaclecs (snake C-type lectins) that inhibit or activate platelets by binding to receptors

Toxicon

Volumn 56, Issue 7, 2010, Pages 1236-1246

  Clemetson, Kenneth J ^a  

^a UNIVERSITY OF BERN   (Switzerland)

Author keywords

C type lectins; Platelets; Receptors; Snaclecs; Snake venom

Indexed keywords

AGGLUCETIN; AGGRETIN; AGKAGGREGIN; AGKISACUTACIN; ALBOAGGREGIN B; ALBOLUXIN; ASPERCETIN; BILINEXIN; BITISCETIN; BOTROCETIN; CONVULXIN; DABOCETIN; ECHICETIN; FLAVOCETIN; GLYCOPROTEIN IB; LECTIN; MAMUSHIGIN; MUCETIN; MUCROCETIN; OPHIOLUXIN; PURPUREOTIN; RHODOAGGRETIN; RISTOCETIN; SNAKE TYPE C TYPE LECTIN; STEJNULXIN; TRIMECETIN; UNCLASSIFIED DRUG; VON WILLEBRAND FACTOR;

AMINO ACID SEQUENCE; BINDING SITE; CARBOXY TERMINAL SEQUENCE; CRYSTAL STRUCTURE; HUMAN; NONHUMAN; PRIORITY JOURNAL; PROTEIN ANALYSIS; PROTEIN BINDING; PROTEIN DETERMINATION; PROTEIN FOLDING; PROTEIN FUNCTION; RECEPTOR BINDING; REVIEW; STRUCTURE ANALYSIS; THROMBOCYTE ACTIVATION; THROMBOCYTE AGGLUTINATION; THROMBOCYTE AGGREGATION;

ANIMALS; BINDING SITES; BLOOD PLATELETS; INTEGRIN ALPHA2BETA1; LECTINS, C-TYPE; MEMBRANE GLYCOPROTEINS; MODELS, MOLECULAR; PLATELET ACTIVATION; PLATELET MEMBRANE GLYCOPROTEINS; PROTEIN STRUCTURE, TERTIARY; SNAKE VENOMS;

ELAPIDAE; HYDROPHIIDAE; SERPENTES; SQUAMATA; VIPERIDAE;

EID: 77957922513     PISSN: 00410101     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.toxicon.2010.03.011     Document Type: Review

References (80)

1. Andrews R.K., Kroll M.H., Ward C.M., Rose J.W., Scarborough R.M., Smith A.I., Lopez J.A., Berndt M.C. Binding of a novel 50-kilodalton alboaggregin from Trimeresurus albolabris and related viper venom proteins to the platelet membrane glycoprotein Ib-IX-V complex. Effect on platelet aggregation and glycoprotein Ib-mediated platelet activation. Biochemistry 1996, 35:12629-12639.
2. Batuwangala T., Leduc M., Gibbins J.M., Bon C., Jones E.Y. Structure of the snake-venom toxin convulxin. Acta Crystallogr. D Biol. Crystallogr. 2004, 60:46-53.
3. Bergmeier W., Bouvard D., Eble J.A., Mokhtari-Nejad R., Schulte V., Zirngibl H., Brakebusch C., Fassler R., Nieswandt B. Rhodocytin (aggretin) activates platelets lacking α2β1 integrin, GPVI, and the ligand binding domain of GPIbα. J. Biol. Chem. 2001, 276:25121-25126.
4. Brinkhous K.M., Read M.S., Fricke W.A., Wagner R.H. Botrocetin (venom coagglutinin): reaction with a broad spectrum of multimeric forms of factor VIII macromolecular complex. Proc. Natl. Acad. Sci. USA 1983, 80:1463-1466.
5. Chang C.H., Chung C.H., Kuo H.L., Hsu C.C., Huang T.F. The highly specific platelet glycoprotein (GP) VI agonist trowaglerix impaired collagen-induced platelet aggregation ex vivo through matrix metalloproteinase-dependent GPVI shedding. J. Thromb. Haemost. 2008, 6:669-676.
6. Chen Y.L., Tsai I.H. Functional and sequence characterization of agkicetin, a new glycoprotein Ib antagonist isolated from Agkistrodon acutus venom. Biochem. Biophys. Res. Commun. 1995, 210:472-477.
7. Chen Y.L., Tsai K.W., Chang T., Hong T.M., Tsai I.H. Glycoprotein Ib-binding protein from the venom of Deinagkistrodon acutus-cDNA sequence, functional characterization, and three-dimensional modeling. Thromb. Haemost. 2000, 83:119-126.
8. Chen Y.S., Huang C.H., Chiou S.H. Toxicon 2009, [Epub ahead of print].
9. Cheng X., Qian Y., Liu Q., Li B.X., Zhang M., Liu J. Purification, characterization, and cDNA cloning of a new fibrinogenlytic venom protein, agkisacutacin, from Agkistrodon acutus venom. Biochem. Biophys. Res. Commun. 1999, 265:530-535.
10. Cheng X., Xu Z.Y., Liu Q.D., Li X.M., Li X.Y., Liu J. Purification and characterization of a platelet agglutinating inhibiting protein (agkisacutacin) from Agkistrodon acutus Venom. Sheng Wu Hua Xue Yu Sheng Wu Wu Li Xue Bao (Shanghai) 2000, 32:653-656.
11. Chiou S.H., Huang K.F., Chow L.P., Tsugita A., Wu S.H. Isolation of a venom factor devoid of proteolytic activity from Taiwan habu (Trimeresurus mucrosquamatus): N-terminal sequence homology and no functional similarity to factors IX/X-binding proteins and botrocetin. J. Protein Chem. 1996, 15:667-674.
12. Chung C.H., Au L.C., Huang T.F. Molecular cloning and sequence analysis of aggretin, a collagen-like platelet aggregation inducer. Biochem. Biophys. Res. Commun. 1999, 263:723-727.
13. Clemetson K.J., Morita T., Kini R.M. Scientific and standardization committee communications: classification and nomenclature of snake venom C-type lectins and related proteins. J. Thromb. Haemost. 2009, 7:360.
14. Dormann D., Clemetson J.M., Navdaev A., Kehrel B.E., Clemetson K.J. Alboaggregin A activates platelets by a mechanism involving glycoprotein VI as well as glycoprotein Ib. Blood 2001, 97:929-936.
15. Du X.Y., Clemetson J.M., Navdaev A., Magnenat E.M., Wells T.N., Clemetson K.J. Ophioluxin, a convulxin-like C-type lectin from Ophiophagus hannah (King cobra) is a powerful platelet activator via glycoprotein VI. J. Biol. Chem. 2002, 277:35124-35132.
16. Du X.Y., Magnenat E., Wells T.N., Clemetson K.J. Alboluxin, a snake C-type lectin from Trimeresurus albolabris venom is a potent platelet agonist acting via GPIb and GPVI. Thromb. Haemost. 2002, 87:692-698.
17. Du X.Y., Navdaev A., Clemetson J.M., Magnenat E., Wells T.N., Clemetson K.J. Bilinexin, a snake C-type lectin from Agkistrodon bilineatus venom agglutinates platelets via GPIb and α2β1. Thromb. Haemost. 2001, 86:1277-1283.
18. Eble J.A., Niland S., Bracht T., Mormann M., Peter-Katalinic J., Pohlentz G., Stetefeld J. The α2β1 integrin-specific antagonist rhodocetin is a cruciform, heterotetrameric molecule. FASEB J. 2009, 23:2917-2927.
19. Eble J.A., Tuckwell D.S. The α2β1 integrin inhibitor rhodocetin binds to the A-domain of the integrin α2 subunit proximal to the collagen-binding site. Biochem. J. 2003, 376:77-85.
20. Flood V.H., Friedman K.D., Gill J.C., Morateck P.A., Wren J.S., Scott J.P., Montgomery R.R. Limitations of the ristocetin cofactor assay in measurement of von Willebrand factor function. J. Thromb. Haemost. 2009, 7:1832-1839.
21. Fry B.G., Vidal N., Norman J.A., Vonk F.J., Scheib H., Ramjan S.F., Kuruppu S., Fung K., Hedges S.B., Richardson M.K., Hodgson W.C., Ignjatovic V., Summerhayes R., Kochva E. Early evolution of the venom system in lizards and snakes. Nature 2006, 439:584-588.
22. Fujimura Y., Ikeda Y., Miura S., Yoshida E., Shima H., Nishida S., Suzuki M., Titani K., Taniuchi Y., Kawasaki T. Isolation and characterization of jararaca GPIb-BP, a snake venom antagonist specific to platelet glycoprotein Ib. Thromb. Haemost. 1995, 74:743-750.
23. Fukuda K., Doggett T., Laurenzi I.J., Liddington R.C., Diacovo T.G. The snake venom protein botrocetin acts as a biological brace to promote dysfunctional platelet aggregation. Nat. Struct. Mol. Biol. 2005, 12:152-159.
24. Fukuda K., Doggett T.A., Bankston L.A., Cruz M.A., Diacovo T.G., Liddington R.C. Structural basis of von Willebrand factor activation by the snake toxin botrocetin. Structure (Camb) 2002, 10:943-950.
25. Fukuda K., Mizuno H., Atoda H., Morita T. Crystal structure of flavocetin-A, a platelet glycoprotein Ib-binding protein, reveals a novel cyclic tetramer of C-type lectin-like heterodimers. Biochemistry 2000, 39:1915-1923.
26. Hamako J., Matsui T., Suzuki M., Ito M., Makita K., Fujimura Y., Ozeki Y., Titani K. Purification and characterization of bitiscetin, a novel von Willebrand factor modulator protein from Bitis arietans snake venom. Biochem. Biophys. Res. Commun. 1996, 226:273-279.
27. Hirotsu S., Mizuno H., Fukuda K., Qi M.C., Matsui T., Hamako J., Morita T., Titani K. Crystal structure of bitiscetin, a von Willebrand factor-dependent platelet aggregation inducer. Biochemistry 2001, 40:13592-13597.
28. Hooley E., Papagrigoriou E., Navdaev A., Pandey A.V., Clemetson J.M., Clemetson K.J., Emsley J. The crystal structure of the platelet activator aggretin reveals a novel (αβ)2 dimeric structure. Biochemistry 2008, 47:7831-7837.
29. Horii K., Brooks M.T., Herr A.B. Convulxin forms a dimer in solution and can bind eight copies of glycoprotein VI: implications for platelet activation. Biochemistry 2009, 48:2907-2914.
30. Horii K., Okuda D., Morita T., Mizuno H. Structural characterization of EMS16, an antagonist of collagen receptor (GPIa/IIa) from the venom of Echis multisquamatus. Biochemistry 2003, 42:12497-12502.
31. Horii K., Okuda D., Morita T., Mizuno H. Crystal structure of EMS16 in complex with the integrin α2-I domain. J. Mol. Biol. 2004, 341:519-527.
32. Howard M.A., Firkin B.G. Ristocetin-a new tool in the investigation of platelet aggregation. Thromb. Diath. Haemorrh. 1971, 26:362-369.
33. Huang K.F., Ko T.P., Hung C.C., Chu J., Wang A.H., Chiou S.H. Crystal structure of a platelet-agglutinating factor isolated from the venom of Taiwan habu (Trimeresurus mucrosquamatus). Biochem. J. 2004, 378:399-407.
34. Jasti J., Paramasivam M., Srinivasan A., Singh T.P. Crystal structure of echicetin from Echis carinatus (Indian saw-scaled viper) at 2.4A resolution. J. Mol. Biol. 2004, 335:167-176.
35. Kanaji S., Kanaji T., Furihata K., Kato K., Ware J.L., Kunicki T.J. Convulxin binds to native, human glycoprotein Ibα (GPIbα). J. Biol. Chem. 2003, 278:39452-39460.
36. Kaneko M.K., Kato Y., Kameyama A., Ito H., Kuno A., Hirabayashi J., Kubota T., Amano K., Chiba Y., Hasegawa Y., Sasagawa I., Mishima K., Narimatsu H. Functional glycosylation of human podoplanin: glycan structure of platelet aggregation-inducing factor. FEBS Lett. 2007, 581:331-336.
37. Kato Y., Kaneko M.K., Kunita A., Ito H., Kameyama A., Ogasawara S., Matsuura N., Hasegawa Y., Suzuki-Inoue K., Inoue O., Ozaki Y., Narimatsu H. Molecular analysis of the pathophysiological binding of the platelet aggregation-inducing factor podoplanin to the C-type lectin-like receptor CLEC-2. Cancer Sci. 2008, 99:54-61.
38. Kawasaki T., Fujimura Y., Usami Y., Suzuki M., Miura S., Sakurai Y., Makita K., Taniuchi Y., Hirano K., Titani K. Complete amino acid sequence and identification of the platelet glycoprotein Ib-binding site of jararaca GPIb-BP, a snake venom protein isolated from Bothrops jararaca. J. Biol. Chem. 1996, 271:10635-10639.
39. Kawasaki T., Taniuchi Y., Hisamichi N., Fujimura Y., Suzuki M., Titani K., Sakai Y., Kaku S., Satoh N., Takenaka T., Handa M., Sawai Y. Tokaracetin, a new platelet antagonist that binds to platelet glycoprotein ib and inhibits von Willebrand factor-dependent shear-induced platelet aggregation. Biochem. J. 1995, 308:947-953.
40. Kerrigan A.M., Dennehy K.M., Mourão-Sá D., Faro-Trindade I., Willment J.A., Taylor P.R., Eble J.A., Reis e Sousa C., Brown G.D. CLEC-2 is a phagocytic activation receptor expressed on murine peripheral blood neutrophils. J. Immunol. 2009, 182:4150-4157.
41. Koh D.C., Armugam A., Jeyaseelan K. Snake venom components and their applications in biomedicine. Cell. Mol. Life Sci. 2006, 63:3030-3041.
42. Kowalska M.A., Tan L., Holt J.C., Peng M., Karczewski J., Calvete J.J., Niewiarowski S. Alboaggregins A and B. Structure and interaction with human platelets. Thromb. Haemost. 1998, 79:609-613.
43. Kunita A., Kashima T.G., Morishita Y., Fukayama M., Kato Y., Tsuruo T., Fujita N. The platelet aggregation-inducing factor aggrus/podoplanin promotes pulmonary metastasis. Am. J. Pathol. 2007, 170:1337-1347.
44. Leduc M., Bon C. Cloning of subunits of convulxin, a collagen-like platelet-aggregating protein from crotalus durissus terrificus venom. Biochem. J. 1998, 333:389-393.
45. Lee W.H., Du X.Y., Lu Q.M., Clemetson K.J., Zhang Y. Stejnulxin, a novel snake C-type lectin-like protein from Trimeresurus stejnegeri venom is a potent platelet agonist acting specifically via GPVI. Thromb. Haemost 2003, 90:662-671.
46. Lee W.H., Zhang Y. Molecular cloning and characterization of a platelet glycoprotein Ib-binding protein from the venom of Trimeresurus stejnegeri. Toxicon 2003, 41:885-892.
47. Li X., Zheng L., Kong C., Kolatkar P.R., Chung M.C. Purpureotin: a novel di-dimeric C-type lectin-like protein from Trimeresurus purpureomaculatus venom is stabilized by noncovalent interactions. Arch. Biochem. Biophys. 2004, 424:53-62.
48. Liu S., Zhu Z., Sun J., Huang Q., Teng M., Niu L. Purification, crystallization and preliminary X-ray crystallographic analysis of agkaggregin, a C-type lectin-like protein from Agkistrodon acutus venom. Acta Crystallogr. D Biol. Crystallogr. 2002, 58:675-678.
49. Lu Q., Navdaev A., Clemetson J.M., Clemetson K.J. GPIb is involved in platelet aggregation induced by mucetin, a snake C-type lectin protein from Chinese habu (Trimeresurus mucrosquamatus) venom. Thromb. Haemost. 2004, 91:1168-1176.
50. Maita N., Nishio K., Nishimoto E., Matsui T., Shikamoto Y., Morita T., Sadler J.E., Mizuno H. Crystal structure of von Willebrand factor A1 domain complexed with snake venom, bitiscetin: insight into glycoprotein Ibα binding mechanism induced by snake venom proteins. J. Biol. Chem. 2003, 278:37777-37781.
51. Marcinkiewicz C., Lobb R.R., Marcinkiewicz M.M., Daniel J.L., Smith J.B., Dangelmaier C., Weinreb P.H., Beacham D.A., Niewiarowski S. Isolation and characterization of EMS16, a C-lectin type protein from Echis multisquamatus venom, a potent and selective inhibitor of the α2β1 integrin. Biochemistry 2000, 39:9859-9867.
52. Mizuno H., Fujimoto Z., Atoda H., Morita T. Crystal structure of an anticoagulant protein in complex with the Gla domain of factor X. Proc. Natl. Acad. Sci. USA 2001, 98:7230-7234.
53. Mizuno H., Fujimoto Z., Koizumi M., Kano H., Atoda H., Morita T. Crystal structure of coagulation factor IX-binding protein from habu snake venom at 2.6A: implication of central loop swapping based on deletion in the linker region. J. Mol. Biol. 1999, 289:103-112.
54. Murakami M.T., Zela S.P., Gava L.M., Michelan-Duarte S., Cintra A.C., Arni R.K. Crystal structure of the platelet activator convulxin, a disulfide-linked α4β4 cyclic tetramer from the venom of Crotalus durissus terrificus. Biochem. Biophys. Res. Commun. 2003, 310:478-482.
55. Navdaev A., Clemetson J.M., Polgar J., Kehrel B.E., Glauner M., Magnenat E., Wells T.N., Clemetson K.J. Aggretin, a heterodimeric C-type lectin from Calloselasma rhodostoma (Malayan pit viper) stimulates platelets by binding to α2β1 integrin and GPIb, activating Syk and PLCγ2, but does not involve the GPVI/Fcγ collagen receptor. J. Biol. Chem. 2001, 276:20882-20889.
56. Navdaev A., Dormann D., Clemetson J.M., Clemetson K.J. Echicetin, a GPIb-binding snake C-type lectin from Echis carinatus, also contains a binding site for IgMκ responsible for platelet agglutination in plasma and inducing signal transduction. Blood 2001, 97:2333-2341.
57. Paaventhan P., Kong C., Joseph J.S., Chung M.C., Kolatkar P.R. Structure of rhodocetin reveals noncovalently bound heterodimer interface. Protein Sci. 2005, 14:169-175.
58. Peng M., Holt J.C., Niewiarowski S. Isolation, characterization and amino acid sequence of echicetin β-subunit, a specific inhibitor of von Willebrand factor and thrombin interaction with glycoprotein Ib. Biochem. Biophys. Res. Commun. 1994, 205:68-72.
59. Peng M., Lu W., Kirby E.P. Alboaggregin-B: a new platelet agonist that binds to platelet membrane glycoprotein Ib. Biochemistry 1991, 30:11529-11536.
60. Peng M., Lu W., Kirby E.P. Characterization of three alboaggregins purified from Trimeresurus albolabris venom. Thromb. Haemost. 1992, 67:702-707.
61. Polgar J., Clemetson J.M., Kehrel B.E., Wiedemann M., Magnenat E.M., Wells T.N.C., Clemetson K.J. Platelet activation and signal transduction by convulxin, a C-type lectin from Crotalus durissus terrificus (tropical rattlesnake) venom via the p62/GPVI collagen receptor. J. Biol. Chem. 1997, 272:13576-13583.
62. Polgar J., Magnenat E.M., Peitsch M.C., Wells T.N., Saqi M.S., Clemetson K.J. Amino acid sequence of the alpha subunit and computer modelling of the alpha and beta subunits of echicetin from the venom of Echis carinatus (saw-scaled viper). Biochem. J. 1997, 323:533-537.
63. Rucavado A., Soto M., Kamiguti A.S., Theakston R.D., Fox J.W., Escalante T., Gutierrez J.M. Characterization of aspercetin, a platelet aggregating component from the venom of the snake Bothrops asper which induces thrombocytopenia and potentiates metalloproteinase-induced hemorrhage. Thromb. Haemost. 2001, 85:710-715.
64. Sakurai Y., Fujimura Y., Kokubo T., Imamura K., Kawasaki T., Handa M., Suzuki M., Matsui T., Titani K., Yoshioka A. The cDNA cloning and molecular characterization of a snake venom platelet glycoprotein Ib-binding protein, mamushigin, from Agkistrodon halys blomhoffii venom. Thromb. Haemost. 1998, 79:1199-1207.
65. Sarray S., Srairi N., Hatmi M., Luis J., Louzir H., Regaya I., Slema H., Marvaldi J., El Ayeb M., Marrakchi N. Lebecetin, a potent antiplatelet C-type lectin from Macrovipera lebetina venom. Biochim. Biophys. Acta 2003, 1651:30-40.
66. Sen U., Vasudevan S., Subbarao G., McClintock R.A., Celikel R., Ruggeri Z.M., Varughese K.I. Crystal structure of the von Willebrand factor modulator botrocetin. Biochemistry 2001, 40:345-352.
67. Shin Y., Okuyama I., Hasegawa J., Morita T. Molecular cloning of glycoprotein Ib-binding protein, flavocetin-A, which inhibits platelet aggregation. Thromb. Res. 2000, 99:239-247.
68. Staniszewska I., Walsh E.M., Rothman V.L., Gaathon A., Tuszynski G.P., Calvete J.J., Lazarovici P., Marcinkiewicz C. Effect of VP12 and viperistatin on inhibition of collagen receptors-dependent melanoma metastasis. Cancer Biol. Ther. 2009, 8:1507-1516.
69. Suzuki-Inoue K., Fuller G.L., García A., Eble J.A., Pöhlmann S., Inoue O., Gartner T.K., Hughan S.C., Pearce A.C., Laing G.D., Theakston R.D., Schweighoffer E., Zitzmann N., Morita T., Tybulewicz V.L., Ozaki Y., Watson S.P. A novel Syk-dependent mechanism of platelet activation by the C-type lectin receptor CLEC-2. Blood 2006, 107:542-549.
70. Taniuchi Y., Kawasaki T., Fujimura Y., Suzuki M., Titani K., Sakai Y., Kaku S., Hisamichi N., Satoh N., Takenaka T., Handa M., Sawai Y. Flavocetin-A and -B, two high molecular mass glycoprotein Ib binding proteins with high affinity purified from Trimeresurus flavoviridis venom, inhibit platelet aggregation at high shear stress. Biochim. Biophys. Acta 1995, 1244:331-338.
71. Uhrin P., Zaujec J., Breuss J.M., Olcaydu D., Chrenek P., Stockinger H., Fuertbauer E., Moser M., Haiko P., Fässler R., Alitalo K., Binder B.R., Kerjaschki D. Novel function for blood platelets and podoplanin in developmental separation of blood and lymphatic circulation. Blood 2010, [Epub ahead of print].
72. Usami Y., Fujimura Y., Suzuki M., Ozeki Y., Nishio K., Fukui H., Titani K. Primary structure of two-chain botrocetin, a von Willebrand factor modulator purified from the venom of Bothrops jararaca. Proc.Natl.Acad.Sci. USA 1993, 90:928-932.
73. 2?. Biochimie 2000, 82:815-831.
74. Wang R., Kini R.M., Chung M.C. Rhodocetin, a novel platelet aggregation inhibitor from the venom of Calloselasma rhodostoma (Malayan pit viper): synergistic and noncovalent interaction between its subunits. Biochemistry 1999, 38:7584-7593.
75. Wang R., Kong C., Kolatkar P., Chung M.C. A novel dimer of a C-type lectin-like heterodimer from the venom of Calloselasma rhodostoma (Malayan pit viper). FEBS Lett. 2001, 508:447-453.
76. Wang W.J., Huang T.F. A novel tetrameric venom protein, agglucetin from Agkistrodon acutus, acts as a glycoprotein Ib agonist. Thromb. Haemost. 2001, 86:1077-1086.
77. Watson A.A., Eble J.A., O'Callaghan C.A. Crystal structure of rhodocytin, a ligand for the platelet-activating receptor CLEC-2. Protein Sci. 2008, 17:1611-1616.
78. Wei Q., Lu Q.M., Jin Y., Li R., Wei J.F., Wang W.Y., Xiong Y.L. Purification and cloning of a novel C-type lectin-like protein with platelet aggregation activity from Trimeresurus mucrosquamatus venom. Toxicon 2002, 40:1331-1338.
79. Zha X.D., Liu J., Xu K.S. cDNA cloning, sequence analysis, and recombinant expression of akitonin beta, a C-type lectin-like protein from Agkistrodon acutus. Acta Pharmacol. Sin. 2004, 25:372-377.
80. Zhong S.R., Jin Y., Wu J.B., Chen R.Q., Jia Y.H., Wang W.Y., Xiong Y.L., Zhang Y. Characterization and molecular cloning of dabocetin, a potent antiplatelet C-type lectin-like protein from Daboia russellii siamensis venom. Toxicon 2006, 47:104-112.