{PDOC00245}
{PS00272; SNAKE_TOXIN}
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* Snake toxins signature *
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Snake toxins belong to  a  family of  proteins [1,2,3]  which groups short and
long neurotoxins, cytotoxins and short toxins, as well as a other miscellanous
venom peptides.  Most  of  these  toxins  act  by  binding  to  the  nicotinic
acetylcholine receptors  in  the postsynaptic membrane of skeletal muscles and
prevent the  binding  of  acetylcholine,  thereby  blocking  the excitation of
muscles.

Snake toxins  are  proteins that consist of sixty to seventy five amino acids.
Among the  invariant  residues  are  eight cysteines all involved in disulfide
bonds. A  signature  pattern  was  developed  [4] which includes four of these
cysteines as    well  as  a  conserved proline thought to be important for the
maintenance of the tertiary structure.   The second cysteine in the pattern is
linked to the third one by a disulfide bond.

-Consensus pattern: G-C-x(1,3)-C-P-x(8,10)-C-C-x(2)-[PDEN]
                    [The 4 C's are involved in disulfide bonds]
-Sequences known to belong to this class detected by the pattern: Most  of the
 snake toxins  are detected except for fasciatoxin, which is an atypical short
 neurotoxin, and eight toxins which have a very low activity.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: May 2004 / Text revised.

[ 1] Dufton M.J.
     "Classification of elapid snake neurotoxins and cytotoxins according
     to chain length: evolutionary implications."
     J. Mol. Evol. 20:128-134(1984).
     PubMed=6433031
[ 2] Endo T., Tamiya N.
     (In) Snake toxins, Harvey A.L., Ed., pp165-222, Pergamon Press, New-York,
     (1991).
[ 3] Mebs D., Claus I.
     (In) Snake toxins, Harvey A.L., Ed., pp425-447, Pergamon Press, New-York,
     (1991).
[ 4] Jonassen I., Collins J.F., Higgins D.G.
     Protein Sci. 4:1587-1595(1995).

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