Structural differences of bacterial and mammalian K+ channels

Area of Science:

• Biophysics
• Molecular Biology
• Structural Biology

Background:

• Voltage-gated potassium channels (Kv channels) are crucial for cellular electrophysiology.
• Kaliotoxin (KTX) is a peptide toxin known to block Kv channels.
• Understanding the structural basis of KTX-Kv channel interaction is key for drug development.

Purpose of the Study:

• To investigate the interaction between kaliotoxin (KTX) and the mammalian potassium channel mKv1.1.
• To elucidate the structural topology of the mKv1.1 pore region using KTX as a probe.
• To identify differences between bacterial and mammalian potassium channel structures.

Main Methods:

• Investigated the pH dependence of KTX block on mKv1.1.
• Utilized site-directed mutagenesis on both KTX and mKv1.1.
• Performed homology modeling of mKv1.1 based on KcsA crystal structure.
• Constrained docking of KTX into the mKv1.1 model.

Main Results:

• KTX block of mKv1.1 was pH-dependent, stronger at acidic external pH.
• Protonation of His(34) in KTX was identified as the cause of pH dependence.
• Specific residues Glu(350) and Glu(353) in mKv1.1 interact with His(34) of KTX.
• Structural modeling revealed differences in the turret region of mKv1.1 compared to KcsA.

Conclusions:

• Mammalian potassium channels possess distinct structural features in the outer pore vestibule (turret) compared to bacterial channels.
• These topological differences influence KTX binding and have implications for rational drug design targeting mammalian Kv channels.