Transmembrane structure of an inwardly rectifying potassium channel

Area of Science:

• Molecular Biology
• Structural Biology
• Biophysics

Background:

• Inwardly rectifying potassium channels (K(ir)) are crucial for regulating physiological processes.
• These channels are composed of four subunits, each with two transmembrane domains (M1 and M2).

Purpose of the Study:

• To identify functional K(ir) 2.1 channels with mutagenized M1 or M2 domains.
• To elucidate the structural arrangement and helix packing within K(ir) channels.

Main Methods:

• Utilized a yeast genetic screen to identify functional K(ir) channels.
• Performed sequence minimization experiments to verify protein-lipid and protein-water interaction surfaces.
• Conducted second-site suppressor analyses to investigate helix packing.

Main Results:

• Identified patterns indicating M1 and M2 domains form helices.
• Determined that M2 pore-lining helices are surrounded by M1 lipid-facing helices.
• Revealed that M1 helices are involved in subunit-subunit interactions.

Conclusions:

• The helix-packing arrangement in K(ir) channels differs from bacterial potassium channels with similar topology.
• Identified conserved helix-packing residues as hallmark sequences for the K(ir) superfamily.