Biophys J, January 2001, p. 215-228, Vol. 80, No. 1

Molecular Determinants of Inactivation within the I-II Linker of 1E (Ca_V2.3) Calcium Channels

Department of Physiology, Membrane Transport Research Group, Université de Montréal, Montréal, Québec H3C 3J7 Canada

Voltage-dependent inactivation of Ca_V2.3 channels was investigated using point mutations in the -subunit-binding site (AID) of the I-II linker. The quintuple mutant 1E N381K + R384L + A385D + D388T + K389Q (NRADK-KLDTQ) inactivated like the wild-type 1E. In contrast, mutations of 1E at position R378 (position 5 of AID) into negatively charged residues Glu (E) or Asp (D) significantly slowed inactivation kinetics and shifted the voltage dependence of inactivation to more positive voltages. When co-injected with 3, R378E inactivated with _inact = 538 ± 54 ms (n = 14) as compared with 74 ± 4 ms (n = 21) for 1E (p < 0.001) with a mid-potential of inactivation E_0.5 = 44 ± 2 mV (n = 10) for R378E as compared with E_0.5 = 64 ± 3 mV (n = 9) for 1E. A series of mutations at position R378 suggest that positively charged residues could promote voltage-dependent inactivation. R378K behaved like the wild-type 1E whereas R378Q displayed intermediate inactivation kinetics. The reverse mutation E462R in the L-type 1C (Ca_V1.2) produced channels with inactivation properties comparable to 1E R378E. Hence, position 5 of the AID motif in the I-II linker could play a significant role in the inactivation of Ca_V1.2 and Ca_V2.3 channels.

Biophys J, January 2001, p. 215-228, Vol. 80, No. 1
© 2001 by the Biophysical Society   0006-3495/01/01/215/14  $2.00

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