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The three-dimensional structure of the toxic peptide Cl13 from the scorpion Centruroides limpidus
Andrea Estefanía López-Giraldo1, Timoteo Olamendi-Portugal2, Lidia Riaño-Umbarila3
1Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, CdMx, 04510, Mexico.
Abstract:
Cl13 is a toxin purified previously from the venom of the Mexican scorpion Centruroides limpidus. This toxin affects the function of voltage gated Na+-channels, human subtypes Nav1.4, Nav1.5 and Nav1.6 in a similar manner as other known β-toxins from scorpion venoms. Here, we report a correction of the primary structure of Cl13, previously published. The peptide does contain 66 amino acids, but residue 58 is a tryptophan and the last C-terminal amino acid is an amidated lysine, instead of arginine. The main contribution of this communication is the determination of the 3D-structure of Cl13, by solution NMR, showing that Cl13 has the classical cysteine-stabilized α/β (CSα/β) folding. It has a triple stranded antiparallel beta sheet commonly present in scorpion sodium channel β-toxins. In addition, we report and discuss a comparison of Cl13 structure with two other toxins (Cn2 and Css2) from scorpions of the same genus Centruroides, which shows important surface similarities with the structure reported here. Finally, the lack of neutralization of Cl13 toxin by two single-chain antibody fragments (scFvs), named LR and 10FG2, which are capable of neutralizing various toxins from Mexican scorpions, is revised. In particular, 10FG2 is capable of neutralizing toxins Cll1 and Cll2 of the same scorpion C. limpidus. The reasons why LR and 10FG2 are unable of neutralizing Cl13 toxin are discussed.
Insights
This study corrects the structure of Cl13 scorpion toxin and reveals its 3D fold, a cysteine-stabilized alpha/beta structure. This toxin affects sodium channels but is not neutralized by certain antibody fragments.
Area of Science:
- Biochemistry and Molecular Biology
- Structural Biology
- Neuroscience
Background:
- Cl13 is a toxin from the Mexican scorpion Centruroides limpidus, known to affect voltage-gated sodium channels (Nav1.4, Nav1.5, Nav1.6).
- Previous structural information on Cl13 requires correction, impacting our understanding of its function and interactions.
Purpose of the Study:
- To correct the primary structure of the Cl13 toxin.
- To determine the three-dimensional (3D) structure of Cl13 using solution NMR.
- To compare the structure of Cl13 with related toxins and investigate its neutralization by antibody fragments.
Main Methods:
- Correction of the primary amino acid sequence of Cl13.
- Determination of the 3D structure of Cl13 via solution Nuclear Magnetic Resonance (NMR) spectroscopy.
- Structural comparison with other Centruroides scorpion toxins (Cn2, Css2) and assessment of neutralization by single-chain antibody fragments (scFvs) LR and 10FG2.
Main Results:
- The primary structure of Cl13 was corrected: it contains 66 amino acids, with tryptophan at residue 58 and a C-terminal amidated lysine.
- Solution NMR revealed that Cl13 adopts a classical cysteine-stabilized alpha/beta (CSα/β) fold with a triple-stranded antiparallel beta sheet, typical for scorpion β-toxins.
- Cl13 shares surface similarities with Cn2 and Css2 toxins; however, scFvs LR and 10FG2, which neutralize other scorpion toxins, failed to neutralize Cl13.
Conclusions:
- The corrected structure and determined 3D fold of Cl13 provide crucial insights into the structure-activity relationships of scorpion β-toxins.
- Structural similarities exist among toxins from the same scorpion genus, but neutralization efficacy by antibodies can vary significantly.
- The inability of specific scFvs to neutralize Cl13 highlights the complexity of toxin-antibody interactions and the need for tailored neutralization strategies.
