Abstract
Calcium plays an essential role as an intracellular second messenger in plants. Rapid increases in [Ca2+]cyt are mediated by calcium channels located on the plasma membrane and endomembranes. In animal cells, it is well known that the α-subunit of L-type Ca2+ channel is composed of 4 domains, each consisting of 6 transmembrane segments and 1 pore loop segment. Recently we reported about a novel plant Ca2+ channel, the A. thaliana AtTPC1, composed of 2 domains. From searching the last available release of the DNA databases, AtTPC1 homologues appear to be well conserved in planta.
AtTPC1 is supposed to function as a dimer and to form an ion channel with 4 domains. A hydrophobic region, between the 2 domains contains 2 EF-hand motifs (EF-1, 2) and possesses weak similarity with the consensus sequence for tetramerization from the animal K+-channels. Mutation D335A in EF-1 increased efficiency of Ca2+ uptake in yeast cells.
