Ancillary protein that assembles as a beta subunit with a voltage-gated potassium channel complex of pore-forming alpha subunits. Modulates the gating kinetics and enhances stability of the channel complex. Assembled with KCNB1 modulates the gating characteristics of the delayed rectifier voltage-dependent potassium channel KCNB1 (PubMed:12954870). Associated with KCNC4/Kv3.4 is proposed to form the subthreshold voltage-gated potassium channel in skeletal muscle and to establish the resting membrane potential (RMP) in muscle cells. Associated with KCNQ1/KCLQT1 may form the intestinal cAMP-stimulated potassium channel involved in chloride secretion that produces a current with nearly instantaneous activation with a linear current-voltage relationship. Interacts with KCNB1. Interacts with KCNC2 (By similarity). Associates with KCNC4/Kv3.4 (PubMed:11207363). Interacts with KCNQ1; produces a current with nearly instantaneous activation with a linear current-voltage relationship and alters membrane raft localization (By similarity) (PubMed:20533308). Colocalizes with KCNB1 at high-density somatodendritic clusters on the surface of hippocampal neurons. Expressed in hippocampal neurons (at protein level) (PubMed:12954870). Widely expressed with highest levels in kidney and moderate levels in small intestine. Belongs to the potassium channel KCNE family. Variant His-83 has been associated with periodic paralysis (PubMed:11207363 and PubMed:12414843). The association could not be confirmed by further studies leading to the conclusion that His-83 does not play a causative role in the disease (PubMed:14504341 and PubMed:15037716).