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Ca 2+ ‐dependent inactivation of the class C L‐type Ca 2+ channel is a property of the α 1 subunit
Author(s) -
Zong Xiangang,
Hofmann Franz
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)01434-9
Subject(s) - protein subunit , class (philosophy) , chemistry , physics , channel (broadcasting) , crystallography , biophysics , stereochemistry , biology , biochemistry , gene , computer science , computer network , artificial intelligence
The stably expressed Ca 2+ channel α 1C‐a and α 1C‐b subunit were used to investigate the molecular basis for Ca 2+ ‐dependent inactivation of the L‐type current. The Ba 2+ current ( I Ba ) of both channels had similar kinetics and inactivated with one time constant of about 400 ms at +20 mV, whereas the Ca 2+ current ( I Ca ) could be fitted only with a bi‐exponential function. The fast ( τ f ) and the slow ( τ s ) time constant were about 20 ms and 400 ms, respectively. The inactivation of I Ca strongly depended on the entry of Ca 2+ as shown by prepulses and variation of the intracellular Ca 2+ chelator. Coexpression of the α 1C subunits with the auxiliary α 2 / δ and β subunits accelerated the voltage‐dependent but not the Ca 2+ ‐dependent inactivation of the channels. These results suggest that the α 1C unit of L‐type Ca 2+ channels itself mediates the Ca 2+ ‐dependent inactivation of the current.