title: Cloning and functional expression of the cDNA encoding an inwardly-rectifying potassium channel expressed in pancreatic beta-cells and in the brain.
abstract: 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.
authors.affiliation: Vollum Institute, Oregon Health Sciences University, Portland 97201, USA.
authors.forename: C T
authors.initials: CT
authors.lastname: Bond
authors.forename: C
authors.initials: C
authors.lastname: Ammälä
authors.forename: R
authors.initials: R
authors.lastname: Ashfield
authors.forename: T A
authors.initials: TA
authors.lastname: Blair
authors.forename: F
authors.initials: F
authors.lastname: Gribble
authors.forename: R N
authors.initials: RN
authors.lastname: Khan
authors.forename: K
authors.initials: K
authors.lastname: Lee
authors.forename: P
authors.initials: P
authors.lastname: Proks
authors.forename: I C
authors.initials: IC
authors.lastname: Rowe
authors.forename: H
authors.initials: H
authors.lastname: Sakura
mesh_terms: 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
chemical_list: D018076:DNA, Complementary; D015221:Potassium Channels