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Biophys J. 1994 Apr;66(4):1068-75.

An engineered cysteine in the external mouth of a K+ channel allows inactivation to be modulated by metal binding.

Author information

1
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts.

Abstract

Substitution of a cysteine in the extracellular mouth of the pore of the Shaker-delta K+ channel permits allosteric inhibition of the channel by Zn2+ or Cd2+ ions at micromolar concentrations. Cd2+ binds weakly to the open state but drives the channel into the slow (C-type) inactivated state, which has a Kd for Cd2+ of approximately 0.2 microM. There is a 45,000-fold increase in affinity when the channel changes from open to inactivated. These results indicate that C-type inactivation involves a structural change in the external mouth of the pore. This structural change is reflected in the T449C mutant as state-dependent metal affinity, which may result either from a change in proximity of the introduced cysteine residues of the four subunits or from a change of the exposure of this residue on the surface of the protein.

PMID:
8038379
PMCID:
PMC1275814
DOI:
10.1016/S0006-3495(94)80888-4
[Indexed for MEDLINE]
Free PMC Article

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