Gating of inwardly rectifying K+ channels localized to a single negatively charged residue.
Inwardly rectifying K+ channels (IRKs) conduct current preferentially in the inward direction. This inward rectification has two components: voltage-dependent blockade by intracellular Mg2+ (Mg2+i) and intrinsic gating. Two members of this channel family, IRK1 (ref. 10) and ROMK1 (ref. 11), differ markedly in affinity for Mg2+i (ref. 12). We found that IRK1 and ROMK1 differ in voltage-dependent gating and searched for the gating structure by large-scale and site-directed mutagenesis. We found that a single amino-acid change within the putative transmembrane domain M2, aspartate (D) in IRK1 to the corresponding asparagine (N) in ROMK1, controls the gating phenotype. Mutation D172N in IRK1 produced ROMK1-like gating whereas the reverse mutation in ROMK1--N171D--produced IRK1-like gating. Thus, a single negatively charged residue seems to be a crucial determinant of gating.
Wible
B A
BA
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030.
Taglialatela
M
M
Ficker
E
E
Brown
A M
AM
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D006801:Humans; D015640:Ion Channel Gating; D008274:Magnesium / Q000378:metabolism; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009865:Oocytes; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014981:Xenopus
C086989:KCNJ1 protein, human; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011993:Recombinant Fusion Proteins; D008274:Magnesium