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Novel Three-Finger Neurotoxins from <i>Naja melanoleuca</i> Cobra Venom Interact with GABA<sub>A</sub> and Nicotinic Acetylcholine Receptors
oleh: Lina Son, Elena Kryukova, Rustam Ziganshin, Tatyana Andreeva, Denis Kudryavtsev, Igor Kasheverov, Victor Tsetlin, Yuri Utkin
Format: | Article |
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Diterbitkan: | MDPI AG 2021-02-01 |
Deskripsi
Cobra venoms contain three-finger toxins (TFT) including α-neurotoxins efficiently binding nicotinic acetylcholine receptors (nAChRs). As shown recently, several TFTs block GABA<sub>A</sub> receptors (GABA<sub>A</sub>Rs) with different efficacy, an important role of the TFTs central loop in binding to these receptors being demonstrated. We supposed that the positive charge (Arg36) in this loop of α-cobratoxin may explain its high affinity to GABA<sub>A</sub>R and here studied α-neurotoxins from African cobra <i>N. melanoleuca</i> venom for their ability to interact with GABAARs and nAChRs. Three α-neurotoxins, close homologues of the known <i>N. melanoleuca</i> long neurotoxins 1 and 2, were isolated and sequenced. Their analysis on <i>Torpedo</i><i>californica</i> and α7 nAChRs, as well as on acetylcholine binding proteins and on several subtypes of GABA<sub>A</sub>Rs, showed that all toxins interacted with the GABA<sub>A</sub>R much weaker than with the nAChR: one neurotoxin was almost as active as α-cobratoxin, while others manifested lower activity. The earlier hypothesis about the essential role of Arg36 as the determinant of high affinity to GABA<sub>A</sub>R was not confirmed, but the results obtained suggest that the toxin loop III may contribute to the efficient interaction of some long-chain neurotoxins with GABA<sub>A</sub>R. One of isolated toxins manifested different affinity to two binding sites on <i>Torpedo</i> nAChR.