Structure of the cytoplasmic β subunit -: T1 assembly of voltage-dependent K+ channels

The structure of the cytoplasmic assembly of voltage-dependent K+ channels was solved by x-ray crystallography at 2.1 angstrom resolution. The assembly includes the cytoplasmic (T1) domain of the integral membrane or subunit together with the oxidoreductase beta subunit in a fourfold symmetric T1(4)beta(4) complex. An electrophysiological assay showed that this complex is oriented with four T1 domains facing the transmembrane pore and four beta subunits facing the cytoplasm. The transmembrane pore communicates with the cytoplasm through lateral, negatively charged openings above the T1(4)beta(4) complex. The inactivation peptides of voltage-dependent K+ channels reach their site of action by entering these openings.