Structure of the cytoplasmic beta 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 assembl y 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 s ubunits 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 reac h their site of action by entering these openings.