Structure-function relationships in scorpion neurotoxins

Sampiéri, Franĉois; Habersetzer-Rochat, Catherine

doi:10.1016/0005-2795(78)90037-5

Cited by 46 publications

(10 citation statements)

References 16 publications

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“…The importance of a positive charge at this position was shown by the decrease in toxicity of the K8A mutant (Table I). Since the electrostatic potential and CD spectrum of the K8A mutant changed only slightly, the decrease in activity did not result from disruption in secondary structure or from elimination of the putative interaction with the adjacent Glu 15 . It is more likely that Lys 8 interacts electrostatically with the receptor site, and since this interaction is part of a multipoint interacting surface (31,36), its effect is rather slim.…”

Section: Discussionmentioning

confidence: 99%

“…3A). It is possible that introduction of two negative charges (Asp 8 and Glu 15 ) at the positive pole disrupts the electrostatic potential of the molecule, whereas one negative charge (Glu 15 in the unmodified toxin, provided that no interaction with Lys 8 exists, or Glu 15 in the K8A mutant, or Asp 8 in the K8D/E15A mutant) is not detrimental. This conclusion is supported by the results obtained with the K8D/ N9D/Y10V triple mutant.…”

Section: Discussionmentioning

confidence: 99%

“…The marked decrease in the apparent binding affinity and toxicity obtained with the K8D mutation (Table I) implied a major role for this residue. This detrimental effect could be due to either direct disruption of a structural motif or indirect alteration generated by repulsion between Asp 8 and Glu 15 , elimination of a direct interaction with a recognition point at the receptor site, and/or alteration of the polarity of the molecule. Analysis of mutants K8A, E15A, and K8D/E15A provided data enabling discrimination among these possibilities.…”

Section: Discussionmentioning

confidence: 99%

“…This substitution was based on results obtained by Delphi calculations with K8D and K8D/E15A computer models suggesting a detrimental effect on the electrostatic potential caused by two adjacent negative charges, i.e. Asp 8 and Glu 15 (Fig. 4, top right).…”

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confidence: 99%

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Identification of Structural Elements of a Scorpion α-Neurotoxin Important for Receptor Site Recognition

Zilberberg

Froy

Loret

et al. 1997

Journal of Biological Chemistry

120

131

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␣-Neurotoxins from scorpion venoms constitute the most studied group of modifiers of the voltage-sensitive sodium channels, and yet, their toxic site has not been characterized. We used an efficient bacterial expression system for modifying specific amino acid residues of the highly insecticidal ␣-neurotoxin Lqh␣IT from the scorpion Leiurus quinquestriatus hebraeus. Toxin variants modified at tight turns, the C-terminal region, and other structurally related regions were subjected to neuropharmacological and structural analyses. This approach highlighted both aromatic (Tyr 10 and Phe 17 ) and positively charged (Lys 8 , Arg 18 , Lys 62 , and Arg 64 ) residues that (i) may interact directly with putative recognition points at the receptor site on the sodium channel; (ii) are important for the spatial arrangement of the toxin polypeptide; and (iii) contribute to the formation of an electrostatic potential that may be involved in biorecognition of the receptor site. The latter was supported by a suppressor mutation (E15A) that restored a detrimental effect caused by a K8D substitution. The feasibility of producing anti-insect scorpion neurotoxins with augmented toxicity was demonstrated by the substitution of the C-terminal arginine with histidine. Altogether, the present study provides for the first time an insight into the putative toxic surface of a scorpion neurotoxin affecting sodium channel gating.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Identification of Structural Elements of a Scorpion α-Neurotoxin Important for Receptor Site Recognition

Zilberberg

Froy

Loret

et al. 1997

Journal of Biological Chemistry

120

131

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“…Another (23). This residue, which also lies on the flat surface of the molecule, is included in Fig.…”

Section: Discussionmentioning

confidence: 99%

Three-dimensional structure of a protein from scorpion venom: a new structural class of neurotoxins.

Fontecilla‐Camps¹,

Almassy²,

Suddath³

et al. 1980

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

103

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The three-dimensional crystal structure of variant-3 toxin from the scorpion Centruroides sculpturatus Ewing has been determined at 3 A resolution. Phases were obtained by use of K2PtCL4 and K2IrCl derivatives. The most prominent secondary structural features are two and a half turns of a-helix and a three-strand stretch of antiparallel a-sheet, which runs parallel to the a-helix. The helix is connected to the middle strand of the a-sheet by two disulfide bridges; a third disulfide bridge is located nearby. Several loops extend out of this dense core of secondary structure. The largest loop is joined to the COOH terminus of the molecule by the fourth disulfide bridge. The overall shape of the molecule resembles a right-hand fist: the a-helix runs along the knuckles of the fist; the a-sheet lies along the second and third joints of the fingers; the thumb is defined by two short loops that are composed of residues 16-21 and residues 41-46; the wrist corresponds to the COOHterminal stretch of residues 52-65 and a loop composed of residues 5-14; and the second joint of the little finger is near the NH2 terminus of the molecule. The a-carbon backbone displays a large flat surface that lies along the second joints of the fingers and the heel of the hand in the fist model. Several of the conserved residues in the scorpion neurotoxins are clustered on this surface, which may play a role in interactions of scorpion toxins with sodium channels of excitable membranes. Scorpion venoms contain sets of small basic proteins that are responsible for the neurotoxic activities of the venoms. These toxins display considerable variations in amino acid composition, but they generally consist of 60-70 amino acids and are crosslinked by four disulfide bridges. The partial or complete primary structures of about 25 toxins, from several different species of scorpions, have been determined (1). The amino acid sequences display a number of common features, including the same general locations of the eight cysteine residues, similar disulfide bridging patterns, and the location of several invariant or conserved residues. Thus, the available chemical data suggest that all of the scorpion toxins probably have similar threedimensional structures.The general effects of whole venoms or purified toxins injected in mammals are those expected from the massive release of neurotransmitters induced by depolarization of the nerve endings (2-4). Despite structural similarities among the various scorpion toxins, these proteins display wide variations in activity (5, 6), and it is not clear if all of the scorpion toxins follow the same general mechanism of action (7). Several of the toxins have been shown to prolong the action potentials of excitable membranes by blocking the inactivation of sodium channels (8-10), an effect similar to that produced by sea anemone toxins (11). However, the scorpion toxin and sea anemone toxin binding sites appear to be distinct from those occupied by otherThe publication costs of this article were defrayed in par...

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Depressant insect selective neurotoxins from scorpion venom: Chemistry, action, and gene cloning

Zlotkin

Gurevitz

Fowler

et al. 1993

Arch Insect Biochem Physiol

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The present study examines the similarity in the symptoms and binding properties between the depressant and excitatory insect-selective neurotoxins, derived from scorpion venom. A comparison of their primary structures and neuromuscular effects is presented. A new depressant toxin (LqhIT2) was purified from the venom of the scorpion Leiurus quinquestriatus hebraeus. The effects of this toxin on a prepupal housefly neuromuscular preparation mimic its effects on the intact insect, i.e, a brief period of repetitive bursts of regular junction potentials (JPs) is followed by reduced amplitude JPs ending with a block of the neuromuscular transmission. "Loose" patch clamp recordings indicate that the repetitive activity has a presynaptic origin (the motor nerve) and resembles the effect of the excitatory toxin AaIT. The final synaptic block is supposed to be the end result of neuronal membrane depolarization. Such an effect is not caused by an excitatory toxin, which induces long "trains" of repetitive firing. The amino acid sequences of three depressant toxins were determined by automatic Edman degradation indicating a high degree of sequence homology. This conservation differs from those of other groups of scorpion toxins. The opposing pharmacological effects of depressant toxins are discussed in light of the above neuromuscular effects and sequence analysis. A genetic approach in the study of the structure-function relationships of the depressant toxins was initiated by isolating cDNA clones encoding the LqhIT2 and BjIT2 toxins. Their sequence analysis revealed the precursor form of these toxins: A 21 amino acid residue signal peptide followed by a 61 amino acid region of the mature toxin, and three additional amino acids at the carboxy terminus.

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Structure-function relationships in scorpion neurotoxins

Cited by 46 publications

References 16 publications

Identification of Structural Elements of a Scorpion α-Neurotoxin Important for Receptor Site Recognition

Identification of Structural Elements of a Scorpion α-Neurotoxin Important for Receptor Site Recognition

Three-dimensional structure of a protein from scorpion venom: a new structural class of neurotoxins.

Depressant insect selective neurotoxins from scorpion venom: Chemistry, action, and gene cloning

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