TY  - JOUR
PY  - 2011//
TI  - Characterization of a new muscarinic toxin from the venom of the Brazilian coral snake Micrurus lemniscatus in rat hippocampus
JO  - Life Sciences
A1  - da Silva, Daniel Coelho
A1  - de Medeiros, Wyara Aparecida Araújo
A1  - Batista, Isabel de Fátima Correia
A1  - Pimenta, Daniel Carvalho
A1  - Lebrun, Ivo
A1  - Abdalla, Fernando Maurício Francis
A1  - Sandoval, Maria Regina Lopes
SP  - 931
EP  - 938
VL  - 89
IS  - 25-26
N2  - AIMS: We have isolated a new muscarinic protein (MT-Mlα) from the venom of the Brazilian coral snake Micrurus lemniscatus. MAIN METHODS: This small protein, which had a molecular mass of 7,048Da, shared high sequence homology with three-finger proteins that act on cholinergic receptors. The first 12 amino acid residues of the N-terminal sequence were determined to be: Leu-Ile-Cys-Phe-Ile-Cys-Phe-Ser-Pro-Thr-Ala-His. KEY FINDINGS: The MT-Mlα was able to displace the [(3)H]QNB binding in the hippocampus of rats. The binding curve in competition experiments with MT-Mlα was indicative of two types of [(3)H]QNB-binding site with pK(i) values of 9.08±0.67 and 6.17±0.19, n=4, suggesting that various muscarinic acetylcholine receptor (mAChR) subtypes may be the target proteins of MT-Mlα. The MT-Mlα and the M(1) antagonist pirenzepine caused a dose-dependent block on total [(3)H]inositol phosphate accumulation induced by carbachol. The IC(50) values for MT-Mlα and pirenzepine were, respectively, 33.1, 2.26nM. Taken together, these studies indicate that the MT-Mlα has antagonist effect on mAChRs in rat hippocampus. SIGNIFICANCE: The results of the present study show, for the first time, that mAChRs function is drastically affected by MT-Mlα since it not only has affinity for mAChRs but also has the ability to inhibit mAChRs.<p />  <p>Language: en</p>
LA  - en
SN  - 0024-3205
UR  - http://dx.doi.org/10.1016/j.lfs.2011.09.024
ID  - ref1
ER  -