NMR Structure and Functional Characteristics of the Hydrophilic N Terminus of the Potassium Channel b-Subunit Kvb1.1*

sium (Kv) channels controls membrane excitability and signal propagation in central neurons and is mediated by protein domains (inactivation gates) occluding the open channel pore from the cytoplasmic side. Inactiva-tion domains (ID) are donated either by the pore-form-ing a-subunit or certain auxiliary b-subunits. Upon co-expression, Kvb1.1 was found to endow non-inactivating members of the Kv1a family with fast inactivation via its unique N terminus. Here we investigated structure and functional properties of the Kvb1.1 N terminus (amino acids 1–62, bN-(1–62)) using NMR spectroscopy and patch clamp recordings. bN-(1–62) showed all hallmarks of N-type inactivation: it inactivated non-inactivating Kv1.1 channels when applied to the cytoplasmic side as a synthetic peptide, and its interaction with the a-sub