Abstract
Calcium plays an essential role as an intracellular second messenger by the transient influx via Ca2+-permeable channels. Recently, putative voltage-gated Ca2+-permeable channels belonging to TPC1 (two pore channel 1) family were cloned from Arabidopsis, tobacco and rice, and revealed that these channels are involved in sugar-sensing, plant defense mechanism and responses to reactive oxygen species. AtTPC1 consists of two homologous domains (I and II), each with six transmembrane segments (S1-6) and a hydrophobic pore region between S5 and S6. The whole structure corresponds to a half molecule of the α1-subunit of L-type voltage-gated Ca2+-channel in animal cells. Interestingly, expression of AtTPC1 significantly promoted a glucose-induced increase in [Ca2+]cyt in the yeast cch1 cells and its Ca2+-permeating activity was disrupted when the EF-hands or Cys residues required for dimerization was mutated. In addition, patch-clamp analysis, an electrophysiological method was performed for the molecular characterization of AtTPC1.
