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Inactivation of gating currents of L-type calcium channels: specific role of the a2d subunit



Inactivation of gating currents of L-type calcium channels: specific role of the a2d subunit



The Journal of General Physiology 111(6): 7-23



The inactivation of intramembranous charge movement in heterologously expressed a1c L-type calcium channels was investigated. Long-lasting depolarization alters the distribution of mobile charge to very negative potentials in rabbit cardiac calcium channels. So-called charge 1 (voltage of half-maximal transfer, V1/2, [approximately equal to] 0 mV) gates noninactivated channels, whereas charge 2 (V1/2 [approximately equal to] -90 mV) is generated in inactivated channels. In a1c/b2a cells, the available charge 1 was reduced upon inactivating depolarization with a time constant, t, of [similar or equal] 8, whereas the available charge 2 was reduced upon recovery from inactivation with a t of [similar or equal] 0.3 s. These processes are thus much slower than charge movement, which takes <50 ms, implying that charges 1 and 2 originate from separate channel modes. The presence of the a2d subunit did not alter the V1/2 of charge 2, but it sped up the reduction of charge 1 upon inactivation at 40 mV and slowed the reduction of charge 2 upon recovery.

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Accession: 009879564

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