{PDOC51863}
{PS51863; LCN_CSAB}
{BEGIN}
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* LCN-type cysteine-stabilized alpha/beta (CS-alpha/beta) domain profile *
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Scorpion venoms  are  complex  mixtures  of  neurotoxins (low molecular weight
proteins), cardiotoxins,  hemolytic  toxins,  antimicrobial  peptides, enzymes
(such as     hyaluronidase,     acetylcholinesterase,     phospholipase    and
metalloproteinases), lipides,  nucleotides,  mucopolysaccharides  and biogenic
amines. Neurotoxins  can  be classified as either short- or long-chain toxins,
which share  a  common  structural  motif,  named  CS-alpha/beta for cysteine-
stabilized alpha-helix/beta-sheet.   Short-chain  neurotoxins  (SCNs)  usually
contain 30-40 residues and three or four disulphide bridges. Most of the short
chain toxins  block  voltage-dependent or Ca(2+)-activated K(+) channels. Most
long-chain neurotoxins  (LCNs)  are  composed of 60-70 residues and are cross-
linked by  four  disulphide  bridges.  The  long chain or voltage-gated sodium
channels scorpion  neurotoxins  (NaScTxs)  can  be classified either as alpha-
toxins, which  slow  down  Na(+)  channel  inactivation, or beta-toxins, which
affect the channel activation process. Both types make the inactivation of the
sodium channel  incomplete  [1,2,3]. Neurotoxins of the birtoxin family can be
included in  the  group of LCNs, although they possess three disulfide bridges
instead of  the usual four disulfide bridges of other members of the group and
they are uniquely shorter than other LCNs [4,5].

The LCN-type  CS-alpha/beta  domain  consists  of one or two short segments of
alpha-helix plus  a  triple-stranded beta-sheet, connected by variable regions
forming loops (turns) (see <PDB:1B3C>) [6]. The beta-sheet and the alpha-helix
are held together by two disulfide bridges.

The profile we developed covers the entire LCN-type CS-alpha/beta domain.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: May 2018 / First entry.

[ 1] Possani L.D., Becerril B., Delepierre M., Tytgat J.
     "Scorpion toxins specific for Na+-channels."
     Eur. J. Biochem. 264:287-300(1999).
     PubMed=10491073
[ 2] Pedraza Escalona M., Possani L.D.
     "Scorpion beta-toxins and voltage-gated sodium channels: interactions
     and effects."
     Front. Biosci. 18:572-587(2013).
     PubMed=23276943
[ 3] Srairi-Abid N., Guijarro J.I., Benkhalifa R., Mantegazza M.,
     Cheikh A., Ben Aissa M., Haumont P.Y., Delepierre M., El Ayeb M.
     "A new type of scorpion Na+-channel-toxin-like polypeptide active on
     K+ channels."
     Biochem. J. 388:455-464(2005).
     PubMed=15656785; DOI=10.1042/BJ20041407
[ 4] Inceoglu B., Lango J., Pessah I.N., Hammock B.D.
     "Three structurally related, highly potent, peptides from the venom of
     Parabuthus  transvaalicus possess divergent biological activity."
     Toxicon 45:727-733(2005).
     PubMed=15804521; DOI=10.1016/j.toxicon.2005.01.020
[ 5] Martin-Eauclaire M.-F., Ceard B., Bosmans F., Rosso J.-P., Tytgat J.,
     Bougis P.E.
     "New 'Birtoxin analogs' from Androctonus australis venom."
     Biochem. Biophys. Res. Commun. 333:524-530(2005).
     PubMed=15963953; DOI=10.1016/j.bbrc.2005.05.148
[ 6] Jablonsky M.J., Jackson P.L., Trent J.O., Watt D.D., Rama Krishna N.
     "Solution structure of a beta-neurotoxin from the New World scorpion
     Centruroides  sculpturatus Ewing."
     Biochem. Biophys. Res. Commun. 254:406-412(1999).
     PubMed=9918851; DOI=10.1006/bbrc.1998.9904

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{END}