1. Cloning and functional expression of the cDNA encoding an inwardly-rectifying potassium channel expressed in pancreatic beta-cells and in the brain
- Author
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Frances M. Ashcroft, I.C.M. Rowe, Rebecca Ashfield, Peter Proks, Chris T. Bond, Raheela N. Khan, Kevin Lee, T. A. Blair, John P. Adelman, Fiona M. Gribble, C Ammälä, H Sakura, and M.J. Ashford
- Subjects
endocrine system ,DNA, Complementary ,Patch-Clamp Techniques ,Potassium Channels ,Protein subunit ,Xenopus ,Molecular Sequence Data ,Biophysics ,Heterologous ,Biology ,Biochemistry ,Islets of Langerhans ,ATP-sensitive K-channel ,Structural Biology ,Complementary DNA ,Genetics ,Diazoxide ,medicine ,Tumor Cells, Cultured ,Animals ,Humans ,Amino Acid Sequence ,Cloning, Molecular ,Pancreatic β-cell ,Molecular Biology ,Peptide sequence ,BIR1 ,Base Sequence ,Inward-rectifier potassium ion channel ,Brain ,Cell Biology ,Molecular biology ,Potassium channel ,Rats ,K-channel ,Inward rectifyer ,Insulinoma ,Heterologous expression ,Sequence Alignment ,medicine.drug - 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 β-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.
- Published
- 1995