Fig. 30.14 Superposition of the binding modes of verapamil 30.26, diltiazem 30.25 and nifedipine 30.24 in the rabbit CaV channel determined by the cryo-EM method. While verapamil and diltiazem bind below the selectivity filter in the central pore and block the passage of calcium ions, nifedipine finds a binding site several angstroms away near the exit port to the membrane. This puts it in contact with the domains of two adjacent voltage sensors. It leads to an indirect allosteric mechanism of pore blockade by dihydropyridines. They are therefore classified as calcium antagonists.