Drysdalin, a snake neurotoxin with higher affinity for soluble acetylcholine binding protein from Aplysia californica than from Lymnaea stagnalis. (November 2020)

• Record Type: Journal Article
• Authors: Chandna, Ritu; Kaczanowska, Katarzyna; Taylor, Palmer; Kini, R.Manjunatha
• Is Part Of: Toxicon. Volume 187(2020)
• Page Start: 86
• Page End: 92
• Publication Date: 2020-11
• Subjects: Site-directed mutagenesis -- Receptor binding -- Snail acetylcholine binding protein -- Nicotinic acetylcholine receptor surrogate; Toxins -- Periodicals; Venom -- Periodicals; 615.9
• DOI: 10.1016/j.toxicon.2020.08.030
• Languages: English
• ISSNs: 0041-0101

Abstract

Abstract: Acetylcholine binding proteins (AChBPs), structural and functional surrogates of the extracellular binding domain of nicotinic acetylcholine receptor (nAChRs), in complex with various antagonists and agonists have provided detailed insights into the neurotransmitter binding site of nAChRs. The classical long-chain α-neurotoxins bungarotoxin (44-fold) and cobratoxin (7-fold) bind to Lymnaea stagnalis (Ls) -AChBP with higher affinity compared to Aplysia californica (Ac) -AChBP. In this study, we describe a novel long chain α-neurotoxin Drysdalin, which has higher binding affinity (7-fold) to Ac -AChBP when compared to Ls -AChBP. This suggests an involvement of different regions or modes of interaction of drysdalin, when compared to the bungarotoxin and cobratoxin. We also found that the C-terminal 24-amino acid residues of drysdalin are critical for the binding to Ac -AChBP and its removal caused ~90-fold reduction in affinity. Further to understand the interaction of drysdalin with Ac -AChBP, we studied the role of three non-conserved amino acid residues of drysdalin, namely Arg30, Leu34 and Ala37. Substitution of Arg30 with the conserved Phe residue caused a ~100-fold reduction, Leu34 with conserved Arg caused a ~6-fold reduction, whereas substitution of Ala37 with conserved Arg enhanced the binding by 3-fold. The dramatic influence of this carboxyl terminal sequence enriched in arginine and proline residues suggests that the toxin binding pose is influenced primarily by this extended sequence. Highlights: Drysdalin, unusual long-chain neurotoxin, binds to Aplysia californica acetylcholine binding protein with high affinity. Arg30 in loop II in drysdalin appears to perfectly substitute Phe30 found in canonical three-finger neurotoxins. C-terminal Arg-Pro repeat sequences contribute to toxin binding to Aplysia californica acetylcholine binding protein.