It was also supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico [CNPq] and FAPESP [Brazilian Government – grants 07/56525-3 to AJZ and 06/02892-2 to WAF Jr.]. AJZ is a post-doctoral fellow and WAF Jr. is a PhD student. We also appreciate the fruitful discussions and suggestions of Dr. Armando IDO inhibitor Alexei Rodríguez Alfonso (CEBIMAR, La Habana, Cuba) in preparation of this manuscript. The sea anemones were collected under the license number 14479-1 of IBAMA from Brazilian Ministry of Environment. “
“Voltage-gated

potassium channels are proteins that allow the passive and selective flux of K+ ions across biological membranes. K+ channels are present in almost all phylogenetic classes and have a broad tissue distribution. These integral membrane proteins are involved in fundamental physiological processes of the cells, playing a major role in a variety of functions, such as cell excitability, control of neurotransmitters release, hormones secretion, regulation of fluid secretion and lymphocyte activation [1]. Selective, high-affinity, modulators of different types of K+ channels are excellent tools to assess the functional role of specific http://www.selleckchem.com/products/r428.html channels. Among these, scorpion neurotoxins

(KTx) are known to inhibit several types of K+ channels. KTxs are 20–95 amino acid peptides stabilized by two, three or four disulfide bonds, which make their tertiary structure highly stable. KTxs have the highly conserved secondary Methocarbamol structural arrangement α/β stabilized by cysteines (CSα/β) and, most of them, have conserved residues which are responsible for block of the ion conduction pore and promote a high affinity binding within the K+ channel pore vestibule, such as a lysine residue and an aromatic residue at 6.6 ± 1.0 Å from the α carbon of that lysine, respectively [10]. Scorpion KTxs were originally classified into three families named α, β and γ [29], all of them have the above mentioned, highly conserved, α/β structural arrangement. Latter, scorpion KTxs presenting a different structural arrangement, with only two α-helices

stabilized by two disulfide bonds, CSα/α, were described, and they were named κ-KTxs [6], [28] and [4]. Among the almost 200 scorpion KTxs described until now (for a complete list see http://www.uniprot.org/docs/scorpktx), the α-KTx family contains about 120 peptides thus far, which are classified in 23 subfamilies, based on their amino acid homology [24], [29] and [32]. Opisthacanthus scorpions belong to the Liochelidae family, and can be found in southern Africa, Central America and South America [18] and, therefore, can be considered a true Gondwana heritage. Currently, this genus comprises 28 species. Work done with the African scorpion O. madagacariensis, described the non-disulfide bridged peptides (NDBPs) ISCT (1501.