 The two central pore domains are combined together from the voltage sensing domains, VSD1 and VSD2.Both the N-terminal domain (NTD) and C-terminal domain (CTD) extend out on the cytosolic side, along with the EF-hand domain in the center that extends into the cytoplasm.The EF-hand domain extends into the cytosol, positioned between VSD1 and VSD2, where it can be activated by cytosolic calcium.