Interacting sites of scorpion toxin ErgTx1 with hERG1 K+ channels

► Eight distinct amino acid mutants were prepared and expressed from toxin ErgTx1. ► Their binding properties towards the human ERG1 potassium channel were determined. ► Amino acids Y14, Y17, F37, M35 are the most important residues for binding. ► Additional to these hydrophobic residues K13 is also important. ► A 3D-structure model of ErgTX1 was prepared showing this face of the toxin.