A new protein glosaxin consisting of non-catalytic domains of type piii metalloproteinase from the venom of pit viper <i>Gloydius saxatilis</i> inhibits nicotinic acetylcholine receptor

Previously, we found that the venom of the pit viper Gloydius saxatilis inhibited the muscle-type nicotinic acetylcholine receptor (nAChR). Using liquid chromatography, a protein glosaxin was isolated from the venom that inhibited the binding of the α-bungarotoxin to the nAChR of muscle type from Torpedo californica. The amino acid sequence of the isolated protein was analyzed by high resolution mass spectrometry. Subsequent bioinformatic analysis showed that it is homologous to the amino acid sequences of disintegrin-like proteins, consisting of non-catalytic domains of type PIII metalloproteinases from the venom of pit vipers of genus Gloydius. A study of the biological activity of the isolated protein showed that it inhibits the binding of α-bungarotoxin to Torpedo californica nAChR with IC50 = 51 μM. The protein also inhibited acetylcholine-induced functional responses of the human neuronal nAChR of α3β2 subtype. This is the first evidence of the ability of proteins consisting of non-catalytic domains of snake venom type PIII metalloproteinase to inhibit the nAChR.