Myotoxin

{{Pfam_box

| Symbol = Myotoxins

| Name = Myotoxin

| image = Crotamin 1H5O.png

| width =

| caption = Structure of crotamine, a Na+ channel affecting toxin from Crotalus durissus terrificus venom.{{cite journal |vauthors=Nicastro G, Franzoni L, de Chiara C, Mancin AC, Giglio JR, Spisni A |title=Solution structure of crotamine, a Na+ channel affecting toxin from Crotalus durissus terrificus venom |journal=Eur. J. Biochem. |volume=270 |issue=9 |pages=1969–79 |date=May 2003 |pmid=12709056 |doi= 10.1046/j.1432-1033.2003.03563.x|doi-access=free }}

| Pfam= PF00819

| InterPro= IPR000881

| SMART=

| Prosite = PDOC00435

| SCOP = 1h5o

| TCDB =

| OPM family=

| OPM protein=

| PDB=

{{PDB3|1h5o}}A:1-42

}}

Myotoxins are small, basic peptides found in snake venoms (e.g. rattlesnakes){{cite journal |vauthors=Griffin PR, Aird SD |title=A new small myotoxin from the venom of the prairie rattlesnake (Crotalus viridis viridis) |journal=FEBS Lett. |volume=274 |issue=1 |pages=43–47 |year=1990 |pmid=2253781 |doi=10.1016/0014-5793(90)81325-I|s2cid=45019479 |doi-access=free |bibcode=1990FEBSL.274...43G }}{{cite journal |vauthors=Samejima Y, Aoki Y, Mebs D |title=Amino acid sequence of a myotoxin from venom of the eastern diamondback rattlesnake (Crotalus adamanteus) |journal=Toxicon |volume=29 |issue=4 |pages=461–468 |year=1991 |pmid=1862521 |doi=10.1016/0041-0101(91)90020-r|bibcode=1991Txcn...29..461S }} and lizard venoms (e.g. Mexican beaded lizard).{{cite journal|last1=Whittington|first1=CM|last2=Papenfuss|first2=AT|last3=Bansal|first3=P|last4=Torres|first4=AM|last5=Wong|first5=ES|last6=Deakin|first6=JE|last7=Graves|first7=T|last8=Alsop|first8=A|last9=Schatzkamer|first9=K|last10=Kremitzki|first10=C|last11=Ponting|first11=CP|last12=Temple-Smith|first12=P|last13=Warren|first13=WC|last14=Kuchel|first14=PW|last15=Belov|first15=K|title=Defensins and the convergent evolution of platypus and reptile venom genes.|journal=Genome Research|date=Jun 2008|volume=18|issue=6|pages=986–94|pmid=18463304|doi=10.1101/gr.7149808|pmc=2413166}} This involves a non-enzymatic mechanism that leads to severe muscle necrosis. These peptides act very quickly, causing instantaneous paralysis to prevent prey from escaping and eventually death due to diaphragmatic paralysis.

The first myotoxin to be identified and isolated was crotamine, from the venom of Crotalus durissus terrificus, a tropical South American rattlesnake, by Brazilian scientist José Moura Gonçalves, in the 1950s. Its biological actions, molecular structure and gene responsible for its synthesis were all elucidated in the last two decades.