Upward movement of IS4 and IIIS4 is a rate-limiting stage in Cav1.2 activation

In order to specify the role of individual S4 segments in CaV1.2 gating, charged residues of segments IS4-IVS4 were replaced by glutamine and the corresponding effects on activation/deactivation of calcium channel currents were analysed. Almost all replacements of charges in IS4 and IIIS4 decreased the slope of the Boltzmann curve of channel activation (activation curve) while charge neutralisations in IIS4 and IVS4 did not significantly affect...