Abstract
BackgroundScorpion toxins are invaluable tools for ion channel research and are potential drugs for human channelopathies. However, it is still an open task to determine the molecular basis underlying the diverse interactions between toxin peptides and ion channels. The inhibitory peptide Maurotoxin (MTX) recognized the distantly related IKCa and Kv1.2 channel with approximately the same potency and using the same functional residues, their differential binding mechanism remain elusive. In this study, we applied computational methods to explore the differential binding modes of MTX to Kv1.2 and IKCa channels, which would help to understand the diversity of channel-toxin interactions and accelerate the toxin-based drug design.ResultsA reasonably stable MTX-IKCa complex was obtained by combining various computational methods and by in-depth comparison with the previous model of the MTX-Kv1.2 complex. Similarly, MTX adopted the β-sheet structure as the interacting surface for binding both channels, with Lys23 occluding the pore. In contrast, the other critical residues Lys27, Lys30, and Tyr32 of MTX adopted distinct interactions when associating with the IKCa channel. In addition, the residues Gln229, Ala230, Ala233, and Thr234 on the IKCa channel turret formed polar and non-polar interactions with MTX, whereas the turret of Kv1.2 was almost not involved in recognizing MTX. In all, the pairs of interacting residues on MTX and the IKCa channel of the bound complex indicated that electrostatic and Van der Waal interactions contributed equally to the formation of a stable MTX-IKCa complex, in contrast to the MTX-Kv1.2 binding that is dominantly mediated by electrostatic forces.ConclusionsDespite sharing similar pharmacological profiles toward both IKCa and Kv1.2 channels, MTX adopted totally diverging modes in the two association processes. All the molecular information unveiled here could not only offer a better understanding about the structural differences between the IKCa and Kv1.2 channels, but also provide novel structural clews that will help in the designing of more selective molecular probes to discriminate between these two channels.
Highlights
Scorpion toxins are invaluable tools for ion channel research and are potential drugs for human channelopathies
Different MTX binding modes towards IKCa and Kv1.2 channels Given the similar blocking activities that MTX showed toward IKCa and Kv1.2 channels [17,18], we first tested whether MTX recognized the IKCa channel in the same binding mode as for the Kv1.2 channel
Through combined computational methods, including ZDOCK, clustering analysis, and molecular dynamics simulation (MDS), a reasonably stable MTX-IKCa complex structure was obtained. Further study of this structure showed that in spite of sharing similar pharmacological profiles toward both IKCa and Kv1.2 channels, MTX associated with the IKCa channel in a quite different mode compared to that of MTX interacting with the Kv1.2 channel
Summary
Scorpion toxins are invaluable tools for ion channel research and are potential drugs for human channelopathies. The inhibitory peptide Maurotoxin (MTX) recognized the distantly related IKCa and Kv1.2 channel with approximately the same potency and using the same functional residues, their differential binding mechanism remain elusive. We applied computational methods to explore the differential binding modes of MTX to Kv1.2 and IKCa channels, which would help to understand the diversity of channel-toxin interactions and accelerate the toxin-based drug design. The widespread use of scorpion-venom peptides acting on K+channels as neuroscience tools and excellent ligand models has tremendously increased our knowledge in many fields, including exploration of the 3-dimensional structures and elucidation of the pharmacological could be a good alternative, which would greatly help to highlight the diversity of channel-toxin interactions and provide structural information for toxin-based drug design. We aimed to interpret the differential binding mechanisms of MTX with reference to the IKCa and Kv1.2 channels, which would provide a deep insight into the topological differences of these two channels and offer important clues for designing inhibitors that are more selective toward the therapeutic IKCa channel
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