PHYSICAL CHEMISTRY AND FUNCTIONAL ASPECTS OF NATIVE AND CHEMICALLY MODIFIED CROTAMINE

Mancin, A. C.(1,2), CECCHINI, A. L. (1,2), ARANTES, E. C. (2), GIGLIO, J. R. (1)

(1)Departamento de Bioquímica e Imunologia, FMRP, USP, (2)Departamento de Física e Química, FCFRP, USP.

Crotalus durissus terrificus snake venom induces serious neurological effects when injected in humans or experimental animals. Unlike several venoms from others species, it doesn’t induce ache or significant tissue destruction in the inoculation area. Victims usually feels a sensation of analgesia around the bite region, which becomes dormant few minutes after the accident and keeps like that for weeks or months.

Crotaminewas first isolated by Gonçalves and Vieira (1950). Injection of crotamine in guinea pigs, mice, rabbits and rats caused paralysis of the hind legs, front legs contracture and breathing difficulties. This toxin has been explored in our laboratory as a molecular model for the design of analgesic drugs since it shows a morphine-like activity when assayed by the hot plate test and acetic acid induced contortion tests.

Chemical modifications of crotamine were able to attenuate or even abolish the hind legs paralysis without significantly decreasing the analgesic activity. Acethylation of the nine Lys residues, which abolished its basic character (PAGE), or reduction and caboxymethylation of the three disulfide bonds, thus destroying its native conformation (Circular Dichroism) were two of such modifications.

These data suggest an important function of the S-S bonds to keep the native conformation. Indeed, spectra of crotamine in the near and far UV, when the S-S bonds are reduced and carboxymethylated, indicate that removing these bonds leads to the loss of secondary and tertiary structures.

Regarding native crotamine, the analgesic effect was shown to be time-dose dependent via opioid receptors, but 50 fold more active than morphine on a pondered basis.

CORRESPONDENCE TO:

Adriana Cristina Mancin, Rua Albert Einstein, no. 1360, Apto. 13 B,  Ribeirão Preto, SP, CEP: 14051-110, Brasil, Email: acmancin@ig.com.br