Cloning and functional expression of the cDNA encoding an inwardly-rectifying potassium channel expressed in pancreatic beta-cells and in the brain.
A cDNA clone encoding an inwardly-rectifying K-channel (BIR1) was isolated from insulinoma cells. The predicted amino acid sequence shares 72% identity with the cardiac ATP-sensitive K-channel rcKATP (KATP-1;[6]). The mRNA is expressed in the brain and insulinoma cells. Heterologous expression in Xenopus oocytes produced currents which were K(+)-selective, time-independent and showed inward rectification. The currents were blocked by external barium and caesium, but insensitive to tolbutamide and diazoxide. In inside-out patches, channel activity was not blocked by 1 mM internal ATP. The sequence homology with KATP-1 suggests that BIR1 is a subunit of a brain and beta-cell KATP channel. However, pharmacological differences and the lack of ATP-sensitivity, suggest that if, this is the case, heterologous subunits must exert strong modulatory influences on the native channel.
Bond
C T
CT
Vollum Institute, Oregon Health Sciences University, Portland 97201, USA.
Ammälä
C
C
Ashfield
R
R
Blair
T A
TA
Gribble
F
F
Khan
R N
RN
Lee
K
K
Proks
P
P
Rowe
I C
IC
Sakura
H
H
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D007340:Insulinoma / Q000378:metabolism; D007515:Islets of Langerhans / Q000378:metabolism*; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000096:biosynthesis / Q000235:genetics*; D051381:Rats; D016415:Sequence Alignment; D014407:Tumor Cells, Cultured; D014981:Xenopus
D018076:DNA, Complementary; D015221:Potassium Channels