Molecular dynamics and functional studies define a hot spot of crystal contacts essential for PcTx1 inhibition of acid-sensing ion channel 1a

Background and Purpose: The spider-venom peptide PcTx1 is the most potent and selective inhibitor of acid-sensing ion channel (ASIC) 1a. It has centrally acting analgesic activity and is neuroprotective in rodent models of ischaemic stroke. Understanding the molecular details of the PcTx1: ASIC1a interaction should facilitate development of therapeutically useful ASIC1a modulators. Previously, we showed that several key pharmacophore residues of PcTx1 reside in a dynamic ß-hairpin loop; conclusions confirmed by recent crystal structures of the complex formed between PcTx1 and chicken ASIC1 (cASIC1). Numerous peptide: channel contacts were observed in these crystal structures, but it remains unclear which of these are functionally important. Experimental Approach: We combined molecular dynamics (MD) simulations of the PcTx1: cASIC1 complex with mutagenesis of PcTx1 and rat ASIC1a. Key Results: Crystal structures of the PcTx1: cASIC1 complex indicated that 15 PcTx1 residues form a total of 57 pairwise intermolecular contacts (