KCNE1 and familial long QT syndrome: Functionally, the co-assembly of KCNE1 with KCNQ1 reproduces most of the characteristics of the delayed rectifier potassium current, IKs, in the heart, although the occurrence of mutations in the other KCNE subunits (2−5) in clinical cases of LQTS (Eldstrom and Fedida, 2011) and lone atrial fibrillation (Olesen et al., 2014) indicate that the full exposition of IKs likely requires a more complete understanding of the contributions of KCNE subunits other than KCNE1 to the channel complex.