Characterisation of calmodulin binding to cyclic nucleotide-gated ion channels from Arabidopsis thaliana

The recently identified cyclic nucleotide-gated ion channels (AtCNGCs) from Arabidopsis have the ability to bind calmodulin, Using two different methods, we mapped the binding site of AtCKGC1 to the last predicted alpha helix of the cyclic nuclcotide binding domain. This is in contrast to CNGCs from animals, where the calmodulin binding site is located in the N-terminus, implying that different mechanisms for CNGC modulation have evolved in animals and plants, Furthermore, we demonstrate that AtCNGC1 and AtCNGC2 have different calmodulin binding affinities and ne provide evidence for target specificities among calmodulin isoforms. (C) 2000 Federation of European Biochemical Societies.