TY - JOUR
T1 - Muscarine-gated K+ channel
T2 - Subunit stoichiometry and structural domains essential for G protein stimulation
AU - Tucker, Stephen J.
AU - Pessia, Maueo
AU - Adelman, John P.
PY - 1996/7
Y1 - 1996/7
N2 - 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.
AB - 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.
KW - G protein sensitivity
KW - cloned subunits
KW - muscarinic channel
KW - stoichiometry
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U2 - 10.1152/ajpheart.1996.271.1.h379
DO - 10.1152/ajpheart.1996.271.1.h379
M3 - Article
AN - SCOPUS:33750811174
SN - 0363-6135
VL - 271
SP - H379-H385
JO - American Journal of Physiology - Heart and Circulatory Physiology
JF - American Journal of Physiology - Heart and Circulatory Physiology
IS - 1 40-1
ER -