G-protein-mediated inhibition of presynaptic voltage-dependent Ca
2+ channels is comprised of voltage-dependent and -resistant components. The former is caused by a direct interaction of Ca
2+ channel α
1 subunits with Gβγ, whereas the latter has not been well characterized. Here, we show that the
N-terminus of Gα
o is critical for the interaction with the
C-terminus of the P/Q-type channel subunit, and that the binding induces voltage-resistant inhibition. A P/Q-type
C-terminal peptide, an antiserum raised against the Gα
o N-terminus, and a Gα
o N-terminal peptide all attenuated the voltage-resistant inhibition of P/Q-type currents. Furthermore, the
N-terminus of Gα
o bound to the
C-terminus of α
1A in vitro, which was prevented either by the P/Q-type channel
C-terminal or Gα
o N-terminal peptide. Although the
C-terminal domain of the
N-type channel showed similar ability to binding with Gα
o N-terminus, the above-mentioned treatments were ineffective in the
N-type channel current. These findings demonstrate that the voltage-resistant inhibition of the P/Q-type channel is caused by the interaction between the
C-terminal domain of the Ca
2+ channel α
1A subunit and the
N-terminal region of Gα
o.
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