Site-directed mutagenesis identified an amino acid residue in the Drosophila Shaker potassium channel that specifically affects intracellular TEA affinity, locating the probable pore-forming region.
Identifies a conserved 18-amino acid region as the probable ion conduction pore of voltage-activated potassium channels.
The active site of voltage-activated potassium channels is a transmembrane aqueous pore that permits ions to permeate the cell membrane in a rapid yet highly selective manner. A useful probe for the pore of potassium-selective channels is the organic ion tetraethylammonium (TEA), which binds with millimolar affinity to the intracellular opening of the pore and blocks potassium current. In the potassium channel encoded by the Drosophila Shaker gene, an amino acid residue that specifically affects the affinity for intracellular TEA has now been identified by site-directed mutagenesis. This residue is in the middle of a conserved stretch of 18 amino acids that separates two locations that are both near the external opening of the pore. These findings suggest that this conserved region is intimately involved in the formation of the ion conduction pore of voltage-activated potassium channels. Further, a stretch of only eight amino acid residues must traverse 80 percent of the transmembrane electric potential difference.
Yellen et al. (1991) studied Potassium channel structure and function. Site-directed mutagenesis was evaluated on Affinity for intracellular TEA. Site-directed mutagenesis identified an amino acid residue in the Drosophila Shaker potassium channel that specifically affects intracellular TEA affinity, locating the probable pore-forming region.