Binding of the G protein betagamma subunit to multiple regions of G protein-gated inward-rectifying K+ channels

FEBS Lett. 1997 Apr 1;405(3):291-8. doi: 10.1016/s0014-5793(97)00197-x.

Abstract

We have previously shown that direct binding of the betagamma subunit of G protein (G betagamma) to both the N-terminal domain and the C-terminal domain of a cloned G protein-gated inward-rectifying K+ channel subunit, GIRK1, is important for channel activation. We have now further localized the G betagamma binding region in the N-terminal domain of GIRK1 to amino acids 34-86 and the G betagamma binding region in the C-terminal domain of GIRK1 to two separate fragments of amino acids 318-374 and amino acids 390-462. Of the four cloned mammalian GIRK subunits, GIRK1-4, GIRK1 and 4 form heteromeric K+ channels in the heart and similar channels in the brain include heteromultimers of GIRK1 and 2, and possibly other GIRK homomultimers and heteromultimers. We found that the N-terminal and the C-terminal domains of all four GIRKs bound G betagamma. The G betagamma binding activities for the C-terminal domains of GIRK2-4 were lower than that for the C-terminal domain of GIRK1. The higher G betagamma binding activity for the C-terminal domain of GIRK1 is due to amino acids 390-462 which are unique to GIRK1. We also found that the N-terminal and C-terminal domains of GIRKs interacted with each other, and the N-terminal domain of either GIRK1 or GIRK4 together with the C-terminal domain of GIRK1 exhibited much enhanced binding of G betagamma. These results are consistent with the idea that the N- and C-terminal domains of the cardiac G protein-gated K+ channel subunits may interact with each other to form higher affinity binding site(s) for G betagamma.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Cattle
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels
  • GTP-Binding Proteins / metabolism*
  • Ion Channel Gating*
  • Macromolecular Substances
  • Molecular Sequence Data
  • Potassium Channels / metabolism*
  • Potassium Channels, Inwardly Rectifying*
  • Protein Binding
  • Recombinant Fusion Proteins
  • Sequence Alignment
  • Sequence Homology, Amino Acid

Substances

  • G Protein-Coupled Inwardly-Rectifying Potassium Channels
  • KCNJ3 protein, human
  • Macromolecular Substances
  • Potassium Channels
  • Potassium Channels, Inwardly Rectifying
  • Recombinant Fusion Proteins
  • GTP-Binding Proteins