GYGD pore motifs in neighbouring potassium channel subunits interact to determine ion selectivity.
Cells maintain a negative resting membrane potential through the constitutive activity of background K+ channels. A novel multigene family of such K+ channels has recently been identified. A unique characteristic of these K+ channels is the presence of two homologous, subunit-like domains, each containing a pore-forming region. Sequence co-variations in the GYGD signature motifs of the two pore regions suggested an interaction between neighbouring pore domains. Mutations of the GYGD motif in the rat drk1 (Kv2.1) K+ channel showed that the tyrosine (Y) position was important for K+ selectivity and single channel conductance, whereas the aspartate (D) position was a critical determinant of open state stability. Tandem constructs engineered to mimic the GYGx-GxGD pattern seen in two-domain K+ channels delineated a co-operative intersubunit interaction between the Y and D positions, which determined ion selectivity, conductance and gating. In the bacterial KcsA K+ channel crystal structure, the equivalent aspartate residue (D80) does not directly interact with permeating K+ ions. However, the data presented here show that the D position is able to fine-tune ion selectivity through a functional interaction with the Y position in the neighbouring subunit. These data indicate a physiological basis for the extensive sequence variation seen in the GYGD motifs of two-domain K+ channels. It is suggested that a cell can precisely regulate its resting membrane potential by selectively expressing a complement of two-domain K+ channels.
Chapman
M L
ML
Department of Pharmacology and Cancer Biology, Duke University Medical Center, PO Box 3813, Durham, NC 27708, USA.
Krovetz
H S
HS
VanDongen
A M
AM
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002463:Cell Membrane Permeability / Q000502:physiology; D051668:Delayed Rectifier Potassium Channels; D005818:Genetic Engineering; D015640:Ion Channel Gating / Q000235:genetics / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000276:immunology*; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D012313:RNA / Q000096:biosynthesis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051669:Shab Potassium Channels; D014443:Tyrosine / Q000378:metabolism
D051668:Delayed Rectifier Potassium Channels; C496991:Kcnb1 protein, rat; D009842:Oligopeptides; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051669:Shab Potassium Channels; C420882:glycyl-tyrosyl-glycyl-aspartate; D014443:Tyrosine; D012313:RNA