Functional influence of the pore helix glutamate in the KcsA K+ channel.
The E71 residue is buried near the selectivity filter in the KcsA K+ channel and forms a carboxyl-carboxylate bridge with D80. We have investigated the importance of E71 by examining neutralization mutants at this position using biochemical and electrophysiological methods. E71 mutations differentially destabilize the detergent-solubilized tetramer; among them, the E71V neutralization mutant has a relatively subtle effect. The E71V channel displays electrical activity when reconstituted into planar lipid bilayers. In single channel recordings, the mutant retains K+/Na+ selectivity, and its conductance in the outward direction is unaltered. Some conduction properties are changed: inward conductance is increased. Our results show that that the E71 side chain is not a primary determinant of ion selectivity or conduction in the wild-type channel, either directly or through the E71:D80 carboxyl-carboxylate bridge.
Choi
HoSook
H
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA.
Heginbotham
Lise
L
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D004926:Escherichia coli / Q000737:chemistry; D008051:Lipid Bilayers / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000235:genetics*; D012964:Sodium / Q000378:metabolism*
D001426:Bacterial Proteins; D008051:Lipid Bilayers; D015221:Potassium Channels; D011994:Recombinant Proteins; C107790:prokaryotic potassium channel; D012964:Sodium; D011188:Potassium