Accessory potassium channel protein which modulates the activity of the pore-forming alpha subunit. Alters functional properties of Kv1.1 and Kv1.2. Forms heteromultimeric complex with alpha subunits. Expression first detected in brain and most anterior regions of spinal cord at embryonic stage 24 (26 hours). By stage 29 (35 hours) expression is also detected in posterior regions of spinal cord. 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.