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Updated: Jul 31, 2026

Mutagenesis and Functional Analysis of Ion Channels Heterologously Expressed in Mammalian Cells
Published on: October 2, 2010
Gating of inwardly rectifying K+ channels localized to a single negatively charged residue
B A Wible1, M Taglialatela, E Ficker
1Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030.
Abstract:
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.
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