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8.B.12.1.5
Omega-ctenitoxin-Pn4a (CnTx-Pn4a; neurotoxin Tx3-6; α1-β toxin) of 90 aas and 1 N-terminal TMS.  The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. It is a potent blocker of high voltage-activated calcium channels, acting mainly on P/Q-type (Cav2.1/CACNA1A) calcium channels and with a minor effect on L- (Cav1/CACNA1) and N-type (Cav2.2/CACNA1B) calcium channels (Vieira et al. 2005). It blocks glutamate release in synaptic transmission mediated by calcium channels (Vieira et al. 2003). The toxin also inhibits the KCl-induced increase of intrasynaptosomal free calcium (Souza et al. 2008).

Accession Number:P81792
Protein Name:Omega-ctenitoxin-Pn4a
Length:90
Molecular Weight:9926.00
Species:Phoneutria nigriventer (Brazilian armed spider) [6918]
Location1 / Topology2 / Orientation3: Secreted1
Substrate

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	MKCAVLFLSV IALVHIFVVE AEEEPDSDAL VPQERACIPR GEICTDDCEC CGCDNQCYCP 
61:	PGSSLGIFKC SCAHANKYFC NRKKEKCKKA