Comparative characterization of two scorpion toxins, BlTx1 and BlTx2, identifies BlTx2 as a Kv4.1-selective peptide

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  Comparative characterization of two scorpion toxins, BlTx1 and BlTx2, identifies BlTx2 as a Kv4.1-selective peptide Abstract Voltage-gated potassium channels of the Kv4 subfamily (Kv4.1, Kv4.2, and Kv4.3) mediate transient A-type potassium currents that regulate neuronal excitability, dendritic integration, and cardiac repolarization. Despite their importance, no pharmacological tool has been available to selectively dissect the role of Kv4.1, as existing peptide toxins from the α-KTx15 family display broad activity across Kv4 isoforms. Here, we report the discovery and characterization of two novel scorpion toxins, BlTx1 and BlTx2, isolated from the venom gland transcriptome of  Buthacus leptochelys . Both toxins were heterologously expressed in yeast and purified to homogeneity. Electrophysiological recordings from  Xenopus laevis  oocytes revealed that BlTx1 and BlTx2 potently inhibited Kv4.1 currents, while sparing Kv4.2 and Kv4.3. Among a panel of 20 tested po...

Venom characterization and structural insights into phospholipase D isoforms from the spider Loxosceles aff. variegata

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Venom characterization and structural insights into phospholipase D isoforms from the spider Loxosceles aff. variegata

Abstract

Brown spider envenomation (loxoscelism) represents a significant public health concern in South America, yet most studies focus on a few medically recognized species. Here, we provide the first molecular and functional characterization of the venom gland extract from Loxosceles aff. variegata (LafvVGE), a brown spider collected in synanthropic habitats in Ituiutaba, Minas Gerais, Brazil. SDS-PAGE and immunoblot analyses revealed prominent protein bands consistent with phospholipase D (PLD) toxins, the main agents of loxoscelism symptoms. ELISA assays demonstrated that LafvVGE is effectively recognized by Brazilian therapeutic antivenoms, indicating immunological cross-reactivity. Enzymatic assays confirmed sphingomyelinase and collagenase/gelatinase activities comparable to those of Loxosceles gaucho (a species of acknowledged medical relevance), although LafvVGE from female individuals showed higher activities than male derived pools under our experimental conditions. Neutralization assays showed complete inhibition of sphingomyelinase activity but only partial inhibition of gelatinase activity by the anti-loxoscelic antivenom, highlighting differential susceptibility of venom components to antivenom-mediated neutralization under in vitro conditions. Molecular analysis of venom gland transcripts identified eight distinct PLD isoforms (LafvPLD1–8), all containing conserved catalytic and metal-binding residues characteristic of class II Loxosceles PLDs. Structural modeling revealed isoform-specific variations in the aromatic cage motif and electrostatic surface, suggesting potential effects on membrane interactions and substrate specificity. Collectively, these findings place L. aff. variegata within the biochemical and structural spectrum of medically relevant Loxosceles species, expanding comparative knowledge of PLD diversity and function. While clinical relevance remains to be established in vivo, this study underscores the value of integrating biochemical, immunological, and structural analyses to identify emerging venom phenotypes with potential implications for surveillance and antivenom coverage.
Silva-Araújo, A. L., Silva-Magalhães, R., Peres-Damásio, P., Pereira, E. H. T., De Oliveira Souza, R., Varela, L. S. D. R. N., Ribeiro Tomé, L. M., Campos de Melo Iani, F., Silveira, A. L., Borges, M. H., Medina-Santos, R., Chavez-Olórtegui, C., Vasconcelos Diniz, M. R., Bittencourt Paiva, A. L., & Guerra-Duarte, C. (2026). Venom characterization and structural insights into phospholipase D isoforms from the spider Loxosceles aff. Variegata. Toxicon, 109129. https://doi.org/10.1016/j.toxicon.2026.109129