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Inhibition of human ether à go‐go potassium channels by Ca 2+ /calmodulin
Author(s) -
Schönherr Roland,
Löber Karsten,
Heinemann Stefan H.
Publication year - 2000
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/19.13.3263
Subject(s) - biology , calmodulin , potassium channel , potassium , biochemistry , biophysics , microbiology and biotechnology , enzyme , chemistry , organic chemistry
Intracellular Ca 2+ inhibits voltage‐gated potassium channels of the ether à go‐go (EAG) family. To identify the underlying molecular mechanism, we expressed the human version hEAG1 in Xenopus oocytes. The channels lost Ca 2+ sensitivity when measured in cell‐free membrane patches. However, Ca 2+ sensitivity could be restored by application of recombinant calmodulin (CaM). In the presence of CaM, half inhibition of hEAG1 channels was obtained in 100 nM Ca 2+ . Overlay assays using labelled CaM and glutathione S ‐transferase (GST) fusion fragments of hEAG1 demonstrated direct binding of CaM to a C‐terminal domain (hEAG1 amino acids 673–770). Point mutations within this section revealed a novel CaM‐binding domain putatively forming an amphipathic helix with both sides being important for binding. The binding of CaM to hEAG1 is, in contrast to Ca 2+ ‐activated potassium channels, Ca 2+ dependent, with an apparent K D of 480 nM. Co‐expression experiments of wild‐type and mutant channels revealed that the binding of one CaM molecule per channel complex is sufficient for channel inhibition.