Status of Asp29 and Asp40 in the Interaction of Naja atra Cardiotoxins with Lipid Bilayers.

Guan-Lin Wu,Liang-Jun Wang,Jing-Ting Chiou,Long-Sen Chang,Yi-Jun Shi,Chia-Hui Huang,Yuan-Chin Lee,Chi-Yu Lu

doi:10.3390/toxins12040262

Abstract

It is widely accepted that snake venom cardiotoxins (CTXs) target the plasma membranes of cells. In the present study, we investigated the role of Asp residues in the interaction of Naja atra cardiotoxin 1 (CTX1) and cardiotoxin 3 (CTX3) with phospholipid bilayers using chemical modification. CTX1 contains three Asp residues at positions 29, 40, and 57; CTX3 contains two Asp residues at positions 40 and 57. Compared to Asp29 and Asp40, Asp57 was sparingly modified with semi-carbazide, as revealed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass and mass/mass analyses. Thus, semi-carbazide-modified CTX1 (SEM-CTX1) mainly contained modified Asp29 and Asp40, while SEM-CTX3 contained modified Asp40. Compared to that of native toxins, trifluoroethanol easily induced structural transition of SEM-CTX1 and SEM-CTX3, suggesting that the structural flexibility of CTXs was constrained by Asp40. Modification of Asp29 and Asp40 markedly promoted the ability of CTX1 to induce permeability of cell membranes and lipid vesicles; CTX3 and SEM-CTX3 showed similar membrane-damaging activity. Modification of Asp residues did not affect the membrane-binding capability of CTXs. Circular dichroism spectra of SEM-CTX3 and CTX3 were similar, while the gross conformation of SEM-CTX1 was distinct from that of CTX1. The interaction of CTX1 with membrane was distinctly changed by Asp modification. Collectively, our data suggest that Asp29 of CTX1 suppresses the optimization of membrane-bound conformation to a fully active state and that the function of Asp40 in the structural constraints of CTX1 and CTX3 is not important for the manifestation of membrane-perturbing activity.

Highlights

Cardiotoxins (CTXs) are major components of Elapidae snake venom and exhibit a variety of pharmacological activities including hemolysis, cardiotoxicity, disruption of muscular integrity, and cytotoxicity [1,2,3,4]
Carboxyl groups in cardiotoxin 1 (CTX1) and cardiotoxin 3 (CTX3) were modified with semi-carbazide
In comparison to CTX1 and CTX3, SEM-CTX1 and SEM-CTX3 showed an increase in mass by 109.6 Da and 62.2 Da, respectively

Summary

Introduction

Cardiotoxins (CTXs) are major components of Elapidae snake venom and exhibit a variety of pharmacological activities including hemolysis, cardiotoxicity, disruption of muscular integrity, and cytotoxicity [1,2,3,4]. The exact mechanisms underlying the broad spectrum of biological. The exact mechanisms underlying the broad spectrum of biological activities have not been fully elucidated. Several studies have suggested that CTXs exert their activities through their membrane perforation ability or through the induction of membrane fusion activities have not been fully elucidated. Several studies have suggested that CTXs exert their activities [5]. CTXs are folded into three -structural loops stabilized by four disulfide bonds. Loops I, II, and through their membrane perforation ability or through the induction of membrane fusion [5].

Methods

Results

Conclusion