Electrostatic interaction between inactivation ball and T1-S1 linker region of Kv1.4 channel

► Mutating negatively charged residues on T1-S1 linker to opposite polar slowed inactivation of Kv1.4 moderately. ► Mutating positively charged residues of inactivation ball to opposite polar slowed inactivation of Kv1.4 strongly. ► Mutating charged residues of both inactivation ball and T1-S1 linker slowed the inactivation compared with Kv1.4WT. ► The voltage-dependence of inactivation was changed, whereas the voltage-dependence of activation was not changed. ► Inserting negatively charged peptide in different positions of inactivation domain slowed the inactivation rate.