Shaker K+ channel T1 domain self-tetramerizes to a stable structure

Area of Science:

• Molecular Biology
• Biophysics
• Structural Biology

Background:

• The T1 domain of potassium channels is critical for the proper assembly of protein subunits.
• Understanding the assembly properties of the Shaker channel T1 domain is essential for elucidating potassium channel function.

Purpose of the Study:

• To investigate the self-assembly capabilities of the Shaker channel T1 domain.
• To determine the stoichiometry (number of subunits, Ns) of the assembled T1 domain multimer.
• To elucidate the mechanism of T1 domain assembly.

Main Methods:

• High-performance liquid chromatography (HPLC) size exclusion chromatography (SEC) was employed to separate T1 domain proteins.
• Co-assembly assays were performed to identify different molecular weight forms.
• Cross-linking of T1 domain proteins followed by HPLC SEC was used to determine multimer stoichiometry.

Main Results:

• HPLC SEC separated T1 domain proteins into monomeric and assembled forms.
• Co-assembly assays confirmed the presence of both monomeric and high molecular weight assembled species.
• Cross-linking and HPLC SEC revealed four evenly spaced bands, indicating a tetrameric assembly.
• The absence of intermediate oligomers suggests the tetramer is the stable assembly state.

Conclusions:

• The Shaker channel T1 domain self-assembles into a stable tetramer.
• The stable tetrameric assembly likely forms a closed ring structure.
• This tetrameric structure is the fundamental unit for T1 domain assembly in potassium channels.