Electrostatic tuning of ion conductance in potassium channels.
Members of the K(+) channel family display remarkable conservation of sequence and structure of the ion selectivity filter, whereas the rates of K(+) turnover vary widely within the family. Here we show that channel conductance is strongly influenced by charge at the channel's intracellular mouth. Introduction of a ring of negative charges at this position in KcsA, a bacterial K(+) channel, augments the conductance in a pH-dependent manner. These results are explained by a simple electrostatic effect based on known channel structures, where the negative charges serve to alter the electrical potential at the inner mouth and, thus, to increase the local K(+) concentration. In addition, removal of the conserved negative charges at equivalent positions in a high-conductance eukaryotic K(+) channel leads to a decrease in conductance.
Nimigean
Crina M
CM
Department of Biochemistry, Howard Hughes Medical Institute, Brandeis University, Waltham, Massachusetts 02454, USA.
Chappie
Joshua S
JS
Miller
Christopher
C
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004553:Electric Conductivity; D004926:Escherichia coli / Q000378:metabolism; D015640:Ion Channel Gating / Q000235:genetics / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D021122:Protein Subunits; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D014982:Xenopus laevis
D001426:Bacterial Proteins; D015221:Potassium Channels; D021122:Protein Subunits; C107790:prokaryotic potassium channel