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Electrostatic interactions between transmembrane segments mediate folding of Shaker K+ channel subunits
S K Tiwari-Woodruff1, C T Schulteis, A F Mock
1Department of Physiology, School of Medicine, University of California, Los Angeles 90095-1751, USA.
Biophysical Journal
|April 1, 1997
Summary
Charged residues in Shaker K+ channels are crucial for protein folding and function. Electrostatic interactions between transmembrane segments S2, S3, and S4 are essential for proper channel structure and gating.
Area of Science:
- Molecular Biology
- Biophysics
- Ion Channel Function
Background:
- Voltage-dependent Shaker K+ channels are critical for neuronal excitability.
- Charged residues in transmembrane segments S2 and S4 are known to be involved in gating charge movement.
Purpose of the Study:
- To investigate structural interactions between transmembrane segments S2, S3, and S4 in Shaker channels.
- To elucidate the role of electrostatic interactions in protein folding and native structure restoration.
Main Methods:
- Employed an intragenic suppression strategy using charge reversal mutations.
- Assessed protein maturation and functional channel restoration after specific mutations.
Main Results:
- Charge reversal mutations in S2 (E283) and S4 (K374) disrupted protein maturation.
- Specific second-site mutations rescued maturation, revealing electrostatic interactions between E283 (S2) and R368/R371 (S4), and K374 (S4) with E293 (S2) and D316 (S3).
- Rescued subunits formed functional channels, indicating native structure restoration.
Conclusions:
- Electrostatic interactions between specific residues in S2, S3, and S4 are vital for proper Shaker K+ channel folding and function.
- These interactions likely persist in the native channel structure.
- The findings suggest a tilted arrangement of the S4 segment relative to S2 and S3 in the voltage-sensing domain.