Muscarine-gated K+ channel: subunit stoichiometry and structural domains essential for G protein stimulation

Am J Physiol. 1996 Jul;271(1 Pt 2):H379-85. doi: 10.1152/ajpheart.1996.271.1.H379.

Abstract

Coexpression in Xenopus oocytes of the cloned cardiac inward rectifier subunits Kir 3.1 and Kir 3.4 results in G protein-stimulated channel activity closely resembling the muscarinic channel underlying the inwardly rectifying K+ current in atrial myocytes. To determine the stoichiometry and relative subunit positions within the channel, Kir 3.1 and Kir 3.4 were coexpressed in varying ratios with cloned G beta 1 gamma 2 subunits and also as tandemly linked tetramers with different relative subunit positions. The results reveal that the most efficient channel comprises two subunits of each type in an alternating array within the tetramer. To localize regions important for subunit coassembly and G protein sensitivity, chimeric subunits containing domains from either Kir 3.1, Kir 3.4, or the G protein-insensitive subunit Kir 4.1 were expressed. The results demonstrate that the transmembrane domains dictate the potentiation of the coassembled channels and that, although the NH4- or COOH-termini of both subunits alone can confer G protein sensitivity, both termini are required for maximal stimulation by G beta 1 gamma 2.

Publication types

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

MeSH terms

  • Animals
  • Cloning, Molecular
  • GTP-Binding Proteins / physiology*
  • Intracellular Membranes / metabolism
  • Ion Channel Gating*
  • Mathematics
  • Muscarine / metabolism*
  • Potassium Channels / chemistry
  • Potassium Channels / metabolism*
  • Xenopus laevis

Substances

  • Potassium Channels
  • Muscarine
  • GTP-Binding Proteins

Grants and funding