An in silico approach to primaquine binding to Trp756 in the external vestibule of sodium channel nav 1.4

Correspondence: eduardo M SalinasStefanón instituto de Fisiología, Benemérita Universidad Autónoma de Puebla 14 Sur 6301, CU, San Manuel, Puebla, Puebla CP 72570, México Tel +222 229 5500 Fax +222 229 5500 ext 7301 email [email protected] Abstract: The aim of our computed study was to examine the possible binding site of primaquine (PQ) using a combined homology protein modeling, automated docking, and experimental approach. The target models of wild type and mutant types of the voltagedependent sodium channel in rat skeletal muscle (rNa v 1.4) were based on previous work by other researchers. Docking was carried out on the P-loop in the structural model of the rNa v 1.4 channel, in the open state configuration, to identify those amino acidic residues important for PQ binding. The three-dimensional models of the P-loop segment of wild types and mutant types (W402, W756C, W1239C, and W1531A at the outer tryptophan-rich lip, as well as D400C, E755C, K1237C, and A1529C of the DEKA motif) helped us to identify residues playing key roles in aminoquinoline binding. In good agreement with experimental results, a 1000-fold inhibition loss was observed. Tryptophan 756 is crucial for the reversible blocking effects of PQ. As a result, mutant-type W756C abolished the blocking effect of PQ in voltage-clamp assays.