The Binding Site of Acetylcholine Receptor as Visualized in the X-Ray Structure of a Complex between α-Bungarotoxin and a Mimotope Peptide

Harel, Michal; Kasher, Roni; Nicolas, Anne; Guss, J. Mitchell; Balass, Moshe; Fridkin, Mati; Smit, August B.; Brejc, Katjuša; Sixma, Titia K.; Katchalski‐Katzir, Ephraim; Sussman, Joel L.; Fuchs, Sara

doi:10.1016/s0896-6273(01)00461-5

Cited by 129 publications

(147 citation statements)

References 46 publications

Supporting

Mentioning

140

Contrasting

Order By: Relevance

“…Clearly the loop C that contains highly functional residues conserved in both receptors plays a predominant binding role. The evidence that supports that conclusion includes (i) mutational analyses with short chain (33,34) and long chain (35)(36)(37) toxins, (ii) the use of synthetic receptor peptides of the region 180-200 (38,39), (iii) studies on the resistance of various species to toxins (40,41), (iv) direct affinity labeling experiments (42), and (v) resolution of solution structures of the complexes formed between ␣-Bgtx and peptides (32,(43)(44)(45). Also, the additional binding function observed here for other ␣ and non-␣ loops was postulated for muscular receptors (46)(47)(48).…”

Section: Discussionmentioning

confidence: 98%

“…However, the manner by which the toxin interacted with the receptor complementary face differed substantially in both studies. In particular, structural clashes appeared in the AChBP-␣-Bgtx complex model (32) between the toxin and the receptor loops D, F, and 1, excluding the possibility that the toxin recognizes the receptor (AChBP) in this conformation.…”

Section: Discussionmentioning

confidence: 99%

“…During the completion of this work, a proposal for the 3D structure of a complex between a snake toxin and AChBP had been reported (32). These authors based their proposition on an observed structural analogy between the AChBP loop C and a mimotope peptide bound to a snake toxin.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Experimentally based model of a complex between a snake toxin and the α7 nicotinic receptor

Fruchart-Gaillard

Gilquin

Antil-Delbeke

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

120

150

View full text Add to dashboard Cite

To understand how snake neurotoxins interact with nicotinic acetylcholine receptors, we have elaborated an experimentally based model of the ␣-cobratoxin-␣7 receptor complex. This model was achieved by using (i) a three-dimensional model of the ␣7 extracellular domain derived from the crystallographic structure of the homologous acetylcholine-binding protein, (ii) the previously solved x-ray structure of the toxin, and (iii) nine pairs of residues identified by cycle-mutant experiments to make contacts between the ␣-cobratoxin and ␣7 receptor. Because the receptor loop F occludes entrance of the toxin binding pocket, we submitted this loop to a dynamics simulation and selected a conformation that allowed the toxin to reach its binding site. T he ␣-neurotoxins from snake venom are potent antagonists that block nicotinic acetylcholine receptors (AChRs) and hence affect synaptic transmission (1-3). Despite many studies (reviewed in ref. 4), the molecular process associated with this efficient blockage remains unclear. To approach this question, we previously studied ␣-cobratoxin (␣-Cbtx), an ␣͞K neurotoxin that binds to both muscular and homopentameric neuronal receptors (␣7 and ␣8) with high affinities (4). This toxin, similar to other snake neurotoxins, is folded into three adjacent loops rich in ␤-sheet that emerge from a small globular core in which four disulfide bonds are located (5). By mutational analyses, the residues by which ␣-Cbtx interacts with the muscular-type or neuronal ␣7 receptors were identified previously (6, 7). The present study shows how functional residues account for the antagonistic properties of the toxin toward the ␣7 neuronal receptor. The ␣7 AChR possesses five identical ␣7 subunits (8) that offer five ligand-binding sites located at the interface of two subunits (9). These sites include residues located on the different functional loops described previously on the principal ␣7 (ϩ) face, loops A, B, and C and on the complementary ␣7 (Ϫ) face, loops D, E, and F (refs. 10-13; see Fig. 1). Until now, the residues of the ␣7 receptor involved in snake toxin binding have remained unknown.The aim of the present paper is fourfold. First, by an extensive mutational study we have identified ␣7 receptor residues involved in the interaction with ␣-Cbtx. Second, by using a double-mutant cycle approach we have disclosed several pairs of interacting residues in the toxin-receptor complex. Third, by using the three-dimensional (3D) structure of an AChBP that is similar functionally and structurally to the N-terminal domain of an AChR ␣-subunit (14), we used a 3D model for the ␣7 subunit extracellular region obtained by comparative modeling [see accompanying paper on page 3210 (15)]. Fourth, by using this model, a molecular dynamics simulation of the loop F region, and the constraints derived from our pairwise analysis, we propose an experimentally based 3D model of the complex between the ␣-Cbtx and ␣7 receptor, which explains the antagonistic properties of the snake toxin toward the neuronal recepto...

show abstract

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Experimentally based model of a complex between a snake toxin and the α7 nicotinic receptor

Fruchart-Gaillard

Gilquin

Antil-Delbeke

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

120

150

View full text Add to dashboard Cite

show abstract

“…Antibodies to the MIR efficiently crosslink adjacent AChRs, not the two ␣1 subunits within an AChR, because the MIR is oriented in a way that only permits crosslinking of adjacent AChRs. Antibodies bound to the MIR do not compete with ligands of the ACh binding site because the binding sites are half way up the side of the AChR at the interface of the plus side of ␣1 subunits and the minus side of ␦ and ⑀ subunits ) and because bound ␣-bungarotoxin occludes only a small area near the ACh binding site (Harel et al, 2001). Thus, the MIR antibodies are not competitive antagonists, and they do not interfere with the binding of 125 I␣-bungarotoxin used to label AChR for immunodiagnostic assays for MG. Antibodies to the MIR are not allosteric antagonists because they bind within one subunit, well away from the channel, and away from subunit interfaces where conformation changes may take place between resting, activated, and desensitized forms of the AChR.…”

Section: Pathological Significance Of the Mirmentioning

confidence: 99%

Autoimmune diseases involving nicotinic receptors

Lindstrom

2002

J. Neurobiol.

View full text Add to dashboard Cite

ABSTRACT:The antibody-mediated autoimmune response to ␣1 muscle nicotinic acetylcholine receptors that causes myasthenia gravis is one of the best characterized autoimmune diseases. Antibodymediated autoimmune responses to neuronal nicotinic receptors are just beginning to be discovered and characterized. One of these causes dysautonomia through antibodies to ␣3 nicotinic receptors of autonomic ganglia. Another causes pemphigus through antibodies to ␣9 nicotinic receptors in skin. Other autoimmune responses to nicotinic receptors may be discovered as the many functional roles of nicotinic receptors are revealed.

show abstract

“…Electrophysiology experiments on the nAChRs expressed in Xenopus oocytes revealed that the first chimera and neurotoxin I block ␣7 nAChRs with similar potency (IC 50 6.1 and 34 nM, respectively). Therefore, the disulfide-confined loop endows neurotoxin II with full activity of long-chain ␣-neurotoxin and the C-terminal tail in neurotoxin I is not essential for binding.…”

mentioning

confidence: 99%

Bacterial Expression, NMR, and Electrophysiology Analysis of Chimeric Short/Long-chain α-Neurotoxins Acting on Neuronal Nicotinic Receptors

Lyukmanova

Шенкарев

Schulga

et al. 2007

Journal of Biological Chemistry

View full text Add to dashboard Cite

Different snake venom neurotoxins block distinct subtypes of nicotinic acetylcholine receptors (nAChR). Short-chain ␣-neurotoxins preferentially inhibit muscle-type nAChRs, whereas longchain ␣-neurotoxins block both muscle-type and ␣7 homooligomeric neuronal nAChRs. An additional disulfide in the central loop of ␣-and -neurotoxins is essential for their action on the ␣7 and ␣3␤2 nAChRs, respectively. Design of novel toxins may help to better understand their subtype specificity. To address this problem, two chimeric toxins were produced by bacterial expression, a short-chain neurotoxin II Naja oxiana with the grafted disulfidecontaining loop from long-chain neurotoxin I from N. oxiana, while a second chimera contained an additional A29K mutation, the most pronounced difference in the central loop tip between long-chain ␣-neurotoxins and -neurotoxins. The correct folding and structural stability for both chimeras were shown by 1 H and 1 H-15 N NMR spectroscopy. Electrophysiology experiments on the nAChRs expressed in Xenopus oocytes revealed that the first chimera and neurotoxin I block ␣7 nAChRs with similar potency (IC 50 6.1 and 34 nM, respectively). Therefore, the disulfide-confined loop endows neurotoxin II with full activity of long-chain ␣-neurotoxin and the C-terminal tail in neurotoxin I is not essential for binding. The A29K mutation of the chimera considerably diminished the affinity for ␣7 nAChR (IC 50 126 nM) but did not convey activity at ␣3␤2 nAChRs. Docking of both chimeras to ␣7 and ␣3␤2 nAChRs was possible, but complexes with the latter were not stable at molecular dynamics simulations. Apparently, some other residues and dimeric organization of -neurotoxins underlie their selectivity for ␣3␤2 nAChRs. Nicotinic acetylcholine receptors (nAChRs)2 belong to the class of ligand-gated ion channels (1-3). All nAChRs are composed of five homologous subunits, which span the plasma membrane to form a transmembrane ion-conducting pore. The muscle-type receptors are composed of four types of subunits, ␣2␤␥␦ in the fetal and ␣2␤⑀␦ in the mature receptor. The best studied nAChR of this type is the receptor from electric organ of ray Torpedo marmorata (4). Neuronal receptors consist of two types of subunits, ␣ (␣2-␣10) and ␤ (␤2-␤4), and can have homooligomeric (for example, ␣7-type nAChR) or heterooligomeric (for example, ␣3␤2-type receptor) composition. Neuronal nAChRs are widely expressed both pre-and postsynaptically, and presynaptic receptors modulate synaptic activity and the release of different neurotransmitters. Neuronal nAChRs are found also in non-neuronal tissues, such as keratinocytes and pulmonary and other tissues (5-8).Because of their role in cellular communication, nAChRs play important roles in the normal functioning of the organism. Dysfunctions of these receptors have been proposed to contribute to a number of disorders of the central and peripheral nervous systems such as schizophrenia, epilepsy, depression, nicotine and alcohol dependence, Alzheimer disease, Parkinson disease, and autis...

show abstract

The Binding Site of Acetylcholine Receptor as Visualized in the X-Ray Structure of a Complex between α-Bungarotoxin and a Mimotope Peptide

Cited by 129 publications

References 46 publications

Experimentally based model of a complex between a snake toxin and the α7 nicotinic receptor

Experimentally based model of a complex between a snake toxin and the α7 nicotinic receptor

Autoimmune diseases involving nicotinic receptors

Bacterial Expression, NMR, and Electrophysiology Analysis of Chimeric Short/Long-chain α-Neurotoxins Acting on Neuronal Nicotinic Receptors

Contact Info

Product

Resources

About