Constructing a covalently linked tandem dimer of the TMEM16A channel. (A) Structure of the nhTMEM16 molecule, showing the positions of corresponding amino acid residues, the mutations of which alter the Ca²⁺ affinity (E698 and E701) and current rectification (K584) of the TMEM16A channel. The nhTMEM16 residues corresponding to K584, E698, and E701 of TMEM16A are N378, E503, and E506, respectively. (B) Schematic diagrams and the nomenclature of various homodimeric and heterodimeric TMEM16A constructs. Red stars represent the E698C mutation.