title: NIP domain prevents N-type inactivation in voltage-gated potassium channels.
abstract: Shaker-related voltage-gated K+ (Kv) channels are assembled from ion-conducting K(v)alpha subunits, which are integral membrane proteins, and auxiliary K(v)beta subunits. This leads to the formation of highly diverse heteromultimeric Kv channels that mediate outward currents with a wide range of time courses for inactivation. Two principal inactivation mechanisms have been recognized: C-type inactivation correlated with carboxy-terminal K(v)alpha-subunit structures, and N-type inactivation conferred by 'ball' domains in the amino termini of certain K(v)alpha and K(v)beta subunits. Assembly of heteromultimers with one or more K(v)alpha- and/or K(v)beta ball domains appears to be an essential principle of the generation of A-type Kv channel diversity. Here we show that, unexpectedly, the presence of K(v)alpha- or K(v)beta-ball domains does not dominate the gating phenotype in heteromultimers containing Kv1.6alpha subunits. These heteromultimers mediate non-inactivating currents because of the dominant-negative activity of a new type of N-type inactivation-prevention (NIP) domain present in the Kv1.6 amino terminus. Mutations in the NIP domain lead to loss of function, and its transfer to another K(v)alpha subunit leads to gain of function. Our discovery of the NIP domain, which neutralizes the activity of K(v)alpha- and K(v)beta-inactivation gates, establishes a new determinant for the gating behaviour of heteromultimeric Kv channels.
authors.affiliation: Zentrum für Molekulare Neurobiologie Hamburg, Institut für Neurale Signalverarbeitung, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Roeper
authors.forename: S
authors.initials: S
authors.lastname: Sewing
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: T
authors.initials: T
authors.lastname: Sommer
authors.forename: S G
authors.initials: SG
authors.lastname: Wanner
authors.forename: O
authors.initials: O
authors.lastname: Pongs
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D004563:Electrochemistry; D004926:Escherichia coli; D015640:Ion Channel Gating; D008969:Molecular Sequence Data; D009154:Mutation; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D051637:Shaker Superfamily of Potassium Channels
chemical_list: D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011993:Recombinant Fusion Proteins; D051637:Shaker Superfamily of Potassium Channels