Data/hora: 11/06/2024 10:54:38

Provedor de dados: | 56
País: | Brazil
Título: | Binding sites and actions of Tx1, a neurotoxin from the venom of the spider Phoneutria nigriventer, in guinea pig ileum
Autores: | Santos,R.G.; Diniz,C.R.; Cordeiro,M.N.; De Lima,M.E.
Data: | 1999-12-01
Ano: | 1999
Palavras-chave: | Phoneutria nigriventer; Spider toxins; Binding; Enteric nervous system; Calcium channels; Guinea pig ileum.
Resumo: | Tx1, a neurotoxin isolated from the venom of the South American spider Phoneutria nigriventer, produces tail elevation, behavioral excitation and spastic paralysis of the hind limbs after intracerebroventricular injection in mice. Since Tx1 contracts isolated guinea pig ileum, we have investigated the effect of this toxin on acetylcholine release, as well as its binding to myenteric plexus-longitudinal muscle membranes from the guinea pig ileum. [125I]-Tx1 binds specifically and with high affinity (Kd = 0.36 ± 0.02 nM) to a single, non-interacting (nH = 1.1), low capacity (Bmax 1.1 pmol/mg protein) binding site. In competition experiments using several compounds (including ion channel ligands), only PhTx2 and PhTx3 competed with [125I]-Tx1 for specific binding sites (K0.5 apparent = 7.50 x 10-4 g/l and 1.85 x 10-5 g/l, respectively). PhTx2 and PhTx3, fractions from P. nigriventer venom, contain toxins acting on sodium and calcium channels, respectively. However, the neurotoxin PhTx2-6, one of the isoforms found in the PhTx2 pool, did not affect [125I]-Tx1 binding. Tx1 reduced the [3H]-ACh release evoked by the PhTx2 pool by 33%, but did not affect basal or KCl-induced [3H]-ACh release. Based on these results, as well as on the homology of Tx1 with toxins acting on calcium channels (&lt;FONT FACE="Symbol"&gt;w&lt;/font&gt;-Aga IA and IB) and its competition with [125I]-&lt;FONT FACE="Symbol"&gt;w&lt;/font&gt;-Cono GVIA in the central nervous system, we suggest that the target site for Tx1 may be calcium channels.
Tipo: | Info:eu-repo/semantics/other
Idioma: | Inglês
Identificador: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X1999001200019
Editor: | Associação Brasileira de Divulgação Científica
Relação: | 10.1590/S0100-879X1999001200019
Formato: | text/html
Fonte: | Brazilian Journal of Medical and Biological Research  v.32 n.12 1999
Fonte: | info:eu-repo/semantics/openAccess