Binding of native κ-neurotoxins and site-directed mutants to nicotinic acetylcholine receptors

Chiappinelli, Vincent A.; Weaver, William R.; McLane, Kathryn E.; Conti‐Fine, Bianca M.; Fiordalisi, James J.; Grant, Gregory A.

doi:10.1016/s0041-0101(96)00110-9

Cited by 57 publications

(30 citation statements)

References 34 publications

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“…6D). Significantly, Arg 33 , reported to be the most crucial residue for the binding of long chain ␣-neurotoxins to ␣7 receptors (23) as well as for -bungarotoxins to bind to neuronal ␣3␤2 receptors (62), is present in candoxin (Arg 35 ). Interestingly, the sequence of WTX (24), which showed poor affinity for both receptors subsets, has only Lys 27 and Lys 50 , which are critical for the muscle ␣␤␥␦ receptor, and Arg 37 , which is involved in the recognition of both receptor types.…”

Section: Discussionmentioning

confidence: 99%

Candoxin, a Novel Toxin from Bungarus candidus, Is a Reversible Antagonist of Muscle (αβγδ) but a Poorly Reversible Antagonist of Neuronal α7 Nicotinic Acetylcholine Receptors

Nirthanan¹,

Charpantier²,

Gopalakrishnakone³

et al. 2002

Journal of Biological Chemistry

104

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In contrast to most short and long chain curaremimetic neurotoxins that produce virtually irreversible neuromuscular blockade in isolated nerve-muscle preparations, candoxin, a novel three-finger toxin from the Malayan krait Bungarus candidus, produced postjunctional neuromuscular blockade that was readily and completely reversible. Nanomolar concentrations of candoxin (IC 50 ‫؍‬ ϳ10 nM) also blocked acetylcholineevoked currents in oocyte-expressed rat muscle (␣␤␥␦) nicotinic acetylcholine receptors in a reversible manner. In contrast, it produced a poorly reversible block (IC 50 ‫؍‬ ϳ50 nM) of rat neuronal ␣7 receptors, clearly showing diverse functional profiles for the two nicotinic receptor subsets. Interestingly, candoxin lacks the helix-like segment cyclized by the fifth disulfide bridge at the tip of the middle loop of long chain neurotoxins, reported to be critical for binding to ␣7 receptors. However, its solution NMR structure showed the presence of some functionally invariant residues involved in the interaction of both short and long chain neurotoxins to muscle (␣␤␥␦) and long chain neurotoxins to ␣7 receptors. Candoxin is therefore a novel toxin that shares a common scaffold with long chain ␣-neurotoxins but possibly utilizes additional functional determinants that assist in recognizing neuronal ␣7 receptors.Curaremimetic or ␣-neurotoxins from snake venoms are well known to bind with high affinity and selectivity and in most instances, almost irreversibly to Torpedo and muscle (␣␤␥␦) nicotinic acetylcholine receptors (nAChR), 1 thereby affecting synaptic neurotransmission and producing flaccid paralysis (1, 2). They belong to a family of proteins called "three-finger toxins," which adopt a flat, leaf-like shape formed by three adjacent loops that emerge from a small globular core, which is the location of the four conserved disulfide bridges (3-9). Other members of this family include -bungarotoxins, which recognize neuronal nicotinic receptors (10), muscarinic toxins with selectivity toward distinct types of muscarinic receptors (11), fasciculins that inhibit acetylcholinesterase (12), calciseptins that block the L-type calcium channels (13,14), cardiotoxins (cytotoxins) that exert their toxicity by forming pores in cell membranes (15), and dendroaspins, which are antagonists of various cell adhesion processes (16). Despite their common structural fold and comparable affinity for the Torpedo and muscle (␣␤␥␦) nAChRs, ␣-neurotoxins are classified as short chain neurotoxins (e.g. erabutoxin-b (Laticauda semifasciata)) that have 60 -62 residues and four conserved disulfide bonds and long chain neurotoxins (e.g. ␣-bungarotoxin (Bungarus multicinctus); ␣-cobratoxin (Naja kaouthia)) with 66 -75 residues and five disulfide bonds (3). The additional disulfide bridge in long chain ␣-neurotoxins, as well in the neuronal -bungarotoxin (B. multicinctus) is located in the middle loop (loop II) (3,8,9). This fifth bridge, which cyclizes a helix-like conformation at the tip of loop II, has been reported to be cru...

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Section: Discussionmentioning

confidence: 99%

Candoxin, a Novel Toxin from Bungarus candidus, Is a Reversible Antagonist of Muscle (αβγδ) but a Poorly Reversible Antagonist of Neuronal α7 Nicotinic Acetylcholine Receptors

Nirthanan¹,

Charpantier²,

Gopalakrishnakone³

et al. 2002

Journal of Biological Chemistry

104

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“…In addition to this, hydrophobic interactions are also involved in the dimer formation [188]. Structure-function relationship studies have shown that Arg-34 and Pro-36 (second loop) are important for binding to neuronal receptors [189]. Similar j-neurotoxins, such as j 2 -neurotoxin and j 3 -neurotoxin from B. multicinctus and j-flavitoxin from I A II A III A I B II B III B I II III I II III b a Fig.…”

Section: Non-covalent Complexesmentioning

confidence: 99%

Protein complexes in snake venom

Doley

Kini

2009

Cell. Mol. Life Sci.

202

125

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Snake venom contains mixture of bioactive proteins and polypeptides. Most of these proteins and polypeptides exist as monomers, but some of them form complexes in the venom. These complexes exhibit much higher levels of pharmacological activity compared to individual components and play an important role in pathophysiological effects during envenomation. They are formed through covalent and/or non-covalent interactions. The subunits of the complexes are either identical (homodimers) or dissimilar (heterodimers; in some cases subunits belong to different families of proteins). The formation of complexes, at times, eliminates the non-specific binding and enhances the binding to the target molecule. On several occasions, it also leads to recognition of new targets as protein-protein interaction in complexes exposes the critical amino acid residues buried in the monomers. Here, we describe the structure and function of various protein complexes of snake venoms and their role in snake venom toxicity.

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“…venoms that inhibit the activity of acetylcholinesterase present at the neuromuscular junction as well as at central synapses (17) and k-neurotoxins (Bungarus spp. ), which bind to neuronal a3b2 as well as other nAChRs composed of b2 subunits (18,19). Several muscarinic toxins have also been isolated from mamba venoms (Dendroaspis spp.…”

Section: Snake Toxins That Affect Cholinergic Neurotransmissionmentioning

confidence: 99%

Three-Finger α-Neurotoxins and the Nicotinic Acetylcholine Receptor, Forty Years On

2004

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Abstract. The discovery, about forty years ago, of a -bungarotoxin, a three-finger a -neurotoxin from Bungarus multicinctus venom, enabled the isolation of the nicotinic acetylcholine receptor (nAChR), making it one of the most thoroughly characterized receptors today. Since then, the sites of interaction between a -neurotoxins and nAChRs have largely been delineated, revealing the remarkable plasticity of the three-finger toxin fold that has optimally evolved to utilize different combinations of functional groups to generate a panoply of target specificities to discern subtle differences between nAChR subtypes. New facets in toxinology have now broadened the scope for the use of a-neurotoxins in scientific discovery. For instance, the development of short, combinatorial library-derived, synthetic peptides that bind with subnanomolar affinity to a -bungarotoxin and prevent its interaction with muscle nAChRs has led to the in vivo neutralization of experimental a -bungarotoxin envenomation, while the successful introduction of pharmatopes bearing "a -bungarotoxin-sensitive sites" into toxin-insensitive nAChRs has permitted the use of various a -neurotoxin tags to localize and characterize new receptor subtypes. More ambitious strategies can now be envisaged for engineering rationally designed novel activities on three-finger toxin scaffolds to generate lead peptides of therapeutic value that target the nicotinic pharmacopoeia. This review details the progress made towards achieving this goal.

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Binding of native κ-neurotoxins and site-directed mutants to nicotinic acetylcholine receptors

Cited by 57 publications

References 34 publications

Candoxin, a Novel Toxin from Bungarus candidus, Is a Reversible Antagonist of Muscle (αβγδ) but a Poorly Reversible Antagonist of Neuronal α7 Nicotinic Acetylcholine Receptors

Candoxin, a Novel Toxin from Bungarus candidus, Is a Reversible Antagonist of Muscle (αβγδ) but a Poorly Reversible Antagonist of Neuronal α7 Nicotinic Acetylcholine Receptors

Protein complexes in snake venom

Three-Finger α-Neurotoxins and the Nicotinic Acetylcholine Receptor, Forty Years On

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