Abstract
Bungarus multicinctus α-bungarotoxin (α-Bgt) and Naja atra cardiotoxins (CTXs) share a common structural scaffold, and their tertiary structures adopt three-fingered loop motifs. Four DNA aptamers against α-Bgt have been reported previously. Given that the binding of aptamers with targeted proteins depends on structural complementarity, in this study, we investigated whether DNA aptamers against α-Bgt could also recognize CTXs. It was found that N. atra cardiotoxin 3 (CTX3) reduced the electrophoretic mobility of aptamers against α-Bgt. Analysis of the changes in the fluorescence intensity of carboxyfluorescein-labeled aptamers upon binding toxin molecules revealed that CTX3 and α-Bgt could bind the tested aptamers. Moreover, the aptamers inhibited the membrane-damaging activity and cytotoxicity of CTX3. In addition to CTX3, other N. atra CTX isotoxins also bound to the aptamer against α-Bgt. Taken together, our data indicate that aptamers against α-Bgt show cross-reactivity with CTXs. The findings that aptamers against α-Bgt also suppress the biological activities of CTX3 highlight the potential utility of aptamers in regard to the broad inhibition of snake venom three-fingered proteins.
Highlights
Aptamers are synthetic oligonucleotides, such as RNA and single-stranded DNA, that can bind to their targets with high affinity and specificity due to their specific secondary or tertiary structures [1,2].A number of studies have suggested the utility of aptamers as diagnostic tools, therapeutic, drug delivery, and biomarker discovery agents, bioimaging tools, and biosensor probes [2]
Aptamers differ from antibodies, they mimic the properties of antibodies in a wide range of biological applications
The four aptamers are designated as bgt1, bgt2, bgt3, and bgt4 in the present study (Table 1)
Summary
Aptamers are synthetic oligonucleotides, such as RNA and single-stranded DNA, that can bind to their targets with high affinity and specificity due to their specific secondary or tertiary structures [1,2]. Snake venom contains a number of pharmacologically-active proteins. Aptamers against β-Bgt can discriminate β-Bgt from other tested snake venom proteins [7]. The tertiary structures of snake venom cardiotoxins (CTXs), short α-neurotoxins, and neurotoxin homologues adopt three-loop motifs, but differ in the extent of their secondary structure and positioning of the invariant side chains [9,10,11,12]. Sequence alignments of long α-neurotoxins, CTXs, short α-neurotoxins, and neurotoxin homologues revealed that these proteins share sequence similarities and their cysteine residues are located at consensus positions [10,13]. One may wonder whether aptamers against α-Bgt can bind three-fingered snake venom proteins owing to complementary molecular surface.
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