Distributed structures underlie gating differences between the kin channel KAT1 and the Kout channel SKOR

Area of Science:

• Plant molecular biology
• Ion channel biophysics
• Cellular physiology

Background:

• Voltage-gated potassium channels are crucial for plant ion homeostasis.
• Inward-rectifying (K(in)) and outward-rectifying (K(out)) channels exhibit distinct gating properties despite structural similarities.
• SKOR and KAT1 are key plant potassium channels with differing functions.

Purpose of the Study:

• To investigate the structural basis of gating differences between K(in) and K(out) channels.
• To identify specific domains responsible for altered gating sensitivity in plant potassium channels.
• To elucidate the role of pore-region helices (S4, S5, S6) in KAT1 and SKOR channel function.

Main Methods:

• Systematic domain swapping experiments between SKOR (K(out)) and KAT1 (K(in)) channels.
• Analysis of channel gating properties following domain alterations.
• Molecular dynamics simulations of KAT1 and SKOR homology models.
• In silico analysis of residue displacement during channel gating.

Main Results:

• The N-terminal portion of the S5 helix significantly impacts the gating of both KAT1 and SKOR channels.
• Molecular dynamics simulations support experimental findings, showing distinct residue movements in KAT1 and SKOR.
• Specific residue displacements in the S5 and S6 segments during gating are more pronounced in KAT1 than SKOR.
• Gating and potassium ion sensing in SKOR are influenced by dispersed structural elements within the S4-S6 region.

Conclusions:

• Gating mechanisms in plant potassium channels are complex and involve multiple structural elements.
• The S5 helix, particularly its N-terminal region, is a critical determinant of gating characteristics in KAT1 and SKOR.
• Dispersed residues across the S4-S6 region collectively regulate channel gating and ion sensing, imposing constraints on conformational changes.