Accessory potassium channel protein which modulates the activity of the pore-forming alpha subunit. All three isoforms alter the functional properties of Kv1.4 and Kv1.5. Isoform KvB1.2 has no effect on Kv1.1, Kv1.2 or Kv2.1. Belongs to the shaker potassium channel beta subunit family. 3 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.