Kaliotoxin (1-37) shows structural differences with related potassium channel blockers

Area of Science:

• Biochemistry
• Structural Biology
• Neuroscience

Background:

• Scorpion toxins are crucial for studying ion channel function.
• Kaliotoxin (KTX) from Androctonus mauretanicus mauretanicus blocks calcium-dependent potassium channels.
• KTX shares homology with other scorpion toxins like charybdotoxin (ChTX) and iberiotoxin (IbTX).

Purpose of the Study:

• To determine the three-dimensional structure of KTX(1-37) using NMR.
• To investigate how KTX's structure, particularly proline-induced alterations, relates to its channel selectivity and blocking activity.
• To compare KTX structure with homologous scorpion toxins.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was employed to determine the structure of KTX(1-37).
• Comparative analysis of KTX structure against known structures of ChTX and IbTX.

Main Results:

• The NMR structure of KTX(1-37) reveals a secondary structure element sequence similar to ChTX.
• The alpha-helical region in KTX is shorter and distorted due to two proline residues.
• A 3(10) helix turn is present in the final three residues of the helical region.
• An extended structure preceding the helix shows altered packing, affecting the accessibility of key residues like 27Lys.

Conclusions:

• KTX possesses a unique three-dimensional structure distinct from ChTX, attributed to proline residues.
• Structural modifications in KTX, including helix distortion and altered packing, likely influence its specific interaction with potassium channels.
• These findings provide insights into the structure-activity relationship of scorpion toxins and their mechanisms of channel modulation.