KCNE1 and atrial fibrillation: To examine whether a mutation in the accessory β-subunit KCNE1 could explain the lone AF phenotype observed in the proband, we expressed wild-type (WT) or mutant KCNE1 together with the pore forming KV7.1 α-subunit in X.laevis oocytes and recorded currents using the two-electrode voltage-clamp technique.