A mouse brain homolog of the Drosophila Shab K+ channel with conserved delayed-rectifier properties.
We have cloned and expressed a mouse brain K+ channel that is the homolog of the Drosophila Shab K+ channel. Mouse and Drosophila Shab K+ channels (mShab and fShab, respectively) represent an instance of K+ channels and structurally related species that are both functionally and structurally conserved; most kinetic, voltage-sensitive, and pharmacological properties are similar for the 2 channels. The greatest functional difference between the currents is recovery from inactivation, which is several times slower for mShab than for fShab currents. In addition to conserved structure, the mShab polypeptide has an unusually long nonconserved region at the carboxyl end of the protein. Truncation of 293 residues from the carboxyl end produced no noticeable change in voltage-sensitive, kinetic, or pharmacological properties. Thus, the measured functional properties of mShab are determined by the remaining 564 residues, most of which are conserved. The mShab and fShab channels are naturally occurring structural variants having substitutions in conserved portions that appear relatively neutral with respect to all measured properties except for, possibly, the rate of recovery from inactivation. The mShab current closely resembles a native delayed-rectifier-type potassium current, IK, in hippocampal neurons.
Pak
M D
MD
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110.
Covarrubias
M
M
Ratcliffe
A
A
Salkoff
L
L
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D001921:Brain / Q000502:physiology*; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins; D015723:Gene Library; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D012689:Sequence Homology, Nucleic Acid; D051669:Shab Potassium Channels; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014982:Xenopus laevis
D029721:Drosophila Proteins; C496990:Kcnb1 protein, mouse; D015221:Potassium Channels; D051669:Shab Potassium Channels; C064033:Shab protein, Drosophila; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; D004247:DNA