Figure 1.

Schematic representation of the four-domain voltage-gated cation channel structure. Functional determinants considered in this work are shown. The pore-forming subunit consists of four homologous domains (D_I–D_IV). Each domain comprises six transmembrane segments (S1–S6). Segments S4 may bear positive charges (+) and function as a voltage sensor. Segments S5 and S6 together with a pore-loop (P-loop) form a pore of a channel. Four amino acid residues, one from each P-loop (white circles), form a selectivity filter. AID – α-interaction domain; CaM – calmodulin; Ca_vβ – auxiliary β-subunit of HVA Ca_v; IG – Na_v-type inactivation gates; IQ – calmodulin-binding region containing pre-IQ and IQ motifs; PM – plasma membrane.