Accessory potassium channel protein which modulates the activity of the pore-forming alpha subunit. Alters the functional properties of Kv1.5. Forms heteromultimeric complex with alpha subunits. Brain specific. Most prominent expression in cerebellum. Weaker signals detected in cortex, occipital lobe, frontal lobe and temporal lobe. Not detected in spinal cord, heart, lung, liver, kidney, pancreas, placenta and skeletal muscle. Alteration of functional properties of alpha subunit is mediated through N-terminal domain of beta subunit. Belongs to the shaker potassium channel beta subunit family.