Binding modes between CTX (Ciguatoxin) and sodium channel, which is one of the targets about CTX toxic effects, were simulated through molecular docking and dynamics method, compared with Quinidine. The docking results indicated that CTX and Quinidine shared different binding modes to sodium channel. The ligand-receptor complexes obtained by molecular docking are stable during 2.5 ns molecular dynamics simulation. Quinidine is tightly held to sodium channel centeral residues of GLU1784 and THR1858 with one hydrogen bond respectively. Its pyridine ring has hydrophobic interactions with residue of PHE1791, which produces the effect of sodium channel block. The binding site of CTX is far away from sodium channel center, one stable hydrogen bond interaction has been formed with residues of SER1782, GLU1784, LEU1786 and GLU1788 respectively. It may promote sodium channel opening and activate sodium channel, and produce its toxic effects.

Key words: molecular docking, molecular dynamics, ciguatoxin, sodium channel protein, mechanism of toxicity