title: A residue W756 in the P-loop segment of the sodium channel is critical for primaquine binding.
abstract: Our study on the wild-type and mutants of the voltage-dependent sodium channel in the rat skeletal muscle Na(v) 1.4 was to examine the possible binding site of primaquine PQ by using an experimental approach. We used a standard voltage-clamp in oocytes. Previously, we had demonstrated that PQ blocks the voltage-dependent sodium current in rat myocytes and that this blocking is concentration-dependent and voltage-independent. The direct-site mutagenesis in the P-loop segment W402C, W756C, W1239C, W1531A at the outer tryptophan-rich lip, and D400C, E758C, K1237C, A1529C of the DEKA locus helped us to identify residues playing a key role in aminoquinoline binding. In full agreement with our computed results, where a 1000-fold reduction of inhibition was measured, the tryptophan 756 is crucial for the reversible modulating effects of PQ. The W756C decreased the blocking effect of PQ in voltage-clamp assays. This new binding site may be important to the development of new drugs that modulate sodium inward currents.
authors.affiliation: Instituto de Fisiología, B.Universidad Autónoma de Puebla, Mexico. salinas@siu.buap.mx
authors.forename: Eduardo M
authors.initials: EM
authors.lastname: Salinas-Stefanon
authors.forename: Evelyn
authors.initials: E
authors.lastname: Martinez-Morales
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Scior
authors.forename: Lourdes
authors.initials: L
authors.lastname: Millan-PerezPeña
mesh_terms: D000818:Animals; D001665:Binding Sites; D005260:Female; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011319:Primaquine / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D015222:Sodium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity; D014364:Tryptophan
chemical_list: D015222:Sodium Channels; D014364:Tryptophan; D011319:Primaquine