Alteration of channel characteristics by exchange of pore-forming regions between two structurally related Ca2+ Channels

Atsuko Yatani, Anthony Bahinski, Minoru Wakamori, Shaoqing Tang, Yasuo Mori, Tsutomu Kobayashi, Arnold Schwartz

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Several types of structurally homologous high voltage-gated Ca2+ channels (L-, P-and N-type) have been identified via biochemical, pharmacological and electrophysiological techniques. Among these channels, the cardiac L-type and the brain BI-2 Ca2+ channel display significantly different biophysical properties. The BI-2 channel exhibits more rapid voltage-dependent current activation and inactivation and smaller single-channel conductance compared to the L-type Ca2+ channel. To examine the molecular basis for the functional differences between the two structurally related Ca2+ channels, we measured macroscopic and single-channel currents from oocytes injected with wild-type and various chimeric channel α1 subunit cRNAs. The results show that a chimeric channel in which the segment between S5-SS2 in repeat IV of the cardiac L-type Ca2+ channel, was replaced by the corresponding region of the BI-2 channel, exhibited macroscopic current activation and inactivation time-courses and single-channel conductance, characteristic of the BI-2 Ca2+ channel. The voltage-dependence of steady-state inactivation was not affected by the replacement. Chimeras, in which the SS2-S6 segment in repeat III or IV of the cardiac channel was replaced by the corresponding BI-2 sequence, exhibited altered macroscopic current kinetics without changes in single-channel conductance. These results suggest that part of the S5-SS2 segment plays a critical role in determining voltage-dependent current activation and inactivation and single-channel conductance and that the SS2-S6 segment may control voltage-dependent kinetics of the Ca2+ channel.

Original languageEnglish
Pages (from-to)93-102
Number of pages10
JournalMolecular and Cellular Biochemistry
Volume140
Issue number2
DOIs
Publication statusPublished - 1994 Nov

Keywords

  • Ca channels
  • chimeras
  • inactivation
  • pore structure

ASJC Scopus subject areas

  • Molecular Biology
  • Clinical Biochemistry
  • Cell Biology

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