Cloning and functional expression of the cDNA encoding an inwardly-rectifying potassium channel expressed in pancreatic beta-cells and in the brain

FEBS Lett. 1995 Jun 19;367(1):61-6. doi: 10.1016/0014-5793(95)00497-w.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Brain / metabolism*
  • Cloning, Molecular
  • DNA, Complementary / genetics
  • DNA, Complementary / isolation & purification
  • Humans
  • Insulinoma / metabolism
  • Islets of Langerhans / metabolism*
  • Molecular Sequence Data
  • Patch-Clamp Techniques
  • Potassium Channels / biosynthesis
  • Potassium Channels / genetics*
  • Rats
  • Sequence Alignment
  • Tumor Cells, Cultured
  • Xenopus


  • DNA, Complementary
  • Potassium Channels

Associated data

  • GENBANK/X83583