Molecular cloning and functional characterization of a novel delayed rectifier potassium channel from channel catfish (Ictalurus punctatus): expression in taste buds.
The gustatory system of channel catfish is widely studied for its sensitivity to amino acids. As a first step in identifying the molecular components that play a role in taste transduction in catfish, we cloned the full-length cDNA for Kv2-catfish, a novel K(+) channel that is expressed in taste buds. The deduced amino acid sequence is 816 residues, and shares a 56-59% sequence identity with Kv2.1 and Kv2.2, the other members of the vertebrate Kv2 subfamily of voltage-gated K(+) channels. The Kv2-catfish RNA was expressed in taste buds, brain, skeletal muscle, kidney, intestine and gills, and its gene is represented as a single copy in the catfish genome. Recombinant channels expressed in Xenopus oocytes were selective for K(+), and were inhibited by tetraethylammonium applied to the extracellular side of the membrane during two-electrode voltage clamp analysis with a 50% inhibitory constant of 6.1 mM. The channels showed voltage-dependent activation, and did not inactivate within 200 ms. Functionally, Kv2-catfish is a voltage-gated, delayed rectifier K(+) channel, and its primary structure is the most divergent sequence identified among the vertebrate members of the Kv2 subfamily of K(+) channels, being related equally well to Kv2.1 and Kv2.2.
Kang
J
J
Monell Chemical Senses Center, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Teeter
J H
JH
Brazier
S P
SP
Nguyen
N D
ND
Chang
C C
CC
Puchalski
R B
RB
D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D018076:DNA, Complementary; D051668:Delayed Rectifier Potassium Channels; D019143:Evolution, Molecular; D007059:Ictaluridae; D017403:In Situ Hybridization; D008564:Membrane Potentials / Q000502:physiology; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D010802:Phylogeny; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D051669:Shab Potassium Channels; D013650:Taste Buds / Q000378:metabolism*; D014982:Xenopus laevis
D018076:DNA, Complementary; D051668:Delayed Rectifier Potassium Channels; C496991:Kcnb1 protein, rat; C496994:Kcnb2 protein, rat; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger; D011994:Recombinant Proteins; D051669:Shab Potassium Channels