Activation of atrial muscarinic K+ channels by low concentrations ofβγ subunits of rat brain G protein
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Effects of G protein βγ subunits from rat brain on cardiac K+ channel was examined in single atrial cells of guinea-pig, using patch clamp techniques. We found that 10 pM concentration of rat brain βγ subunits preparation could activate the atrial muscarine receptor-gated K+ channel (IK.ACh). Neither the detergent, CHAPS, used to suspend βγ nor the boiled βγ preparation activated IK.ACh. Furthermore, preincubation of βγ subunits preparation in Mg2+-free solution, which easily inactivated α-GTP-γS, did not affect βγ-activation of IK.ACh. We concluded, therefore, that βγ subunits themselves can activate IK.ACh.
Key Wordsmuscarine receptor-gated K+ channel GTP-binding protein subunits cardiac atrial cells
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