Structural component of a potassium channel. Mediates the potassium permeability of membranes; potassium current is regulated by CaMKII and CASK. Has a role in growth of the perineurial glial layer of the larval peripheral nerve. The voltage-dependent potassium channel is a heterotetramer of potassium channel proteins (By similarity). Interaction with CASK. Eag recruits CASK to the plasma membrane. Expressed in the axon and the terminal boutons of motor neurons. When in complex with CASK, the efficiency of Thr-787 phosphorylation is increased. Increased growth of the perineurial glial layer of the larval peripheral nerve. Hyperexcitability at the larval neuromuscular junction (NMJ) and memory formation defects in the adult. The segment S4 is probably the voltage-sensor and is characterized by a series of positively charged amino acids at every third position. The segment H5 is thought to line the channel pore. Belongs to the potassium channel family. H (Eag) (TC 1.A.1.20) subfamily. Eag sub-subfamily.