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The amino side of the C‐terminus determines fast inactivation of the T‐type calcium channel α 1G
Author(s) -
Staes Mik,
Talavera Karel,
Klugbauer Norbert,
Prenen Jean,
Lacinová Lubica,
Droogmans Guy,
Hofmann Franz,
Nilius Bernd
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.0035m.x
Subject(s) - chemistry , n terminus , linker , c terminus , amino acid , transfection , stereochemistry , intracellular , hek 293 cells , biophysics , calcium , calcium channel , biochemistry , peptide sequence , biology , receptor , gene , organic chemistry , computer science , operating system
1 We analysed the kinetic properties of the fast inactivating T‐type calcium channel α 1G in HEK 293 cells transfected with different α 1G chimeras, containing the N‐terminus, III‐IV linker or various C‐terminal regions of the slowly inactivating L‐type α 1C . 2 A highly negatively charged region of 23 amino acids at the amino side of the intracellular carboxy terminus of α 1G was found to be critical for fast inactivation. 3 The N‐terminus of α 1G does not seem to be necessary for inactivation of the T‐type calcium channel because replacement of the α 1G N‐terminus with the α 1C N‐terminus did not influence channel kinetics at all. 4 Replacing the III‐IV linker of α 1G with that of α 1C decreased the rate of inactivation at ‐20 mV from 15.8 ± 1.8 to 8.5 ± 1.1 ms, and shifted the potential for half‐maximal inactivation from ‐69.6 ± 0.8 to ‐54.0 ± 1.7 mV. However, these parameters were not significantly different at other potentials. 5 We suggest a putative ‘ball‐and‐chain’‐like mechanism for inactivation in which the negative charges function as an acceptor domain for a ball, hypothetically located at a different intracellular part of the channel. In addition, transferring the IQ motif and EF hand of α 1C to α 1G does not confer Ca 2+ ‐dependent inactivation on α 1G , suggesting that other sequences besides the C‐terminus are needed for Ca 2+ ‐dependent inactivation of α 1C .