Functions as a voltage-gated inward-rectifying Ca(2+) channel (VDCC) across the plasma membrane that mediates sucrose-induced Ca(2+) influx in autotrophically grown leaf cells. Acts as the major ROS-responsive Ca(2+) channel and is the possible target of Al-dependent inhibition. Plays a regulatory role in defense responses (By similarity). Inhibited by Al(3+). Homodimer. Each of the two internal repeats contains five hydrophobic transmembrane segments (S1, S2, S3, S5, S6) and one positively charged transmembrane segment (S4). S4 segments probably represent the voltage-sensor and are characterized by a series of positively charged amino acids (By similarity). Belongs to the calcium channel alpha-1 subunit (TC 1.A.1.11) family. Two pore calcium channel subfamily.