Electrostatic interactions of S4 voltage sensor in Shaker K+ channel

Area of Science:

• Molecular Biology
• Biophysics
• Ion Channel Function

Background:

• The S4 segment is a key component of the voltage sensor in Shaker K+ channels.
• Understanding electrostatic interactions is vital for elucidating voltage-dependent activation mechanisms.

Purpose of the Study:

• To identify electrostatic interactions involving the S4 segment important for Shaker K+ channel voltage-dependent activation.
• To investigate the role of specific charged residues in channel structure and function.

Main Methods:

• Utilized a strategy analogous to intragenic suppression without genetic selection.
• Introduced single and double point mutations in Shaker K+ channel constructs.
• Assessed protein maturation and folding of mutant channels.

Main Results:

• Neutralization mutations K374Q and R377Q in the S4 segment impaired protein maturation, indicating a role in proper folding.
• Second site mutations E293Q (S2 segment) and D316N (S3 segment) specifically rescued the K374Q mutation.
• Identified a network of strong, local electrostatic interactions involving K374, E293, and D316 that stabilize channel structure.
• Weak, long-range electrostatic interactions were also suggested by other double mutant combinations.

Conclusions:

• A network of local electrostatic interactions, including K374, E293, and D316, stabilizes the Shaker K+ channel structure.
• These interactions likely play a significant role in the voltage-dependent activation mechanism.
• Proposed a structural hypothesis explaining the impact of these interactions on channel conformation stability.