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

Stephen J. Tucker, Maueo Pessia, John Adelman

Research output: Contribution to journalArticle

Abstract

Coexpression in Xenopus oocytes of the cloned cardiac inward rectifier subunits K(ir) 3.1 and K(ir) 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, K(ir). 3.1 and K(ir) 3.4 were eoexpressed in varying ratios with cloned Gβ1γ2 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 K(ir) 3.1, K(ir) 3.4, or the G protein- insensitive subunit K(ir) 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 Gβ1γ2.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume271
Issue number1 40-1
Publication statusPublished - Jul 1996

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Keywords

  • cloned subunits
  • G protein sensitivity
  • muscarinic channel
  • stoichiometry

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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