Cytoplasmic potassium channel subunit that modulates the characteristics of the channel-forming alpha-subunits (PubMed:
7499366, PubMed:
7603988, PubMed:
17156368, PubMed:
17540341, PubMed:
19713757). Modulates action potentials via its effect on the pore-forming alpha subunits (By similarity). Promotes expression of the pore-forming alpha subunits at the cell membrane, and thereby increases channel activity (By similarity). Mediates closure of delayed rectifier potassium channels by physically obstructing the pore via its N-terminal domain and increases the speed of channel closure for other family members (PubMed:
9763623). Promotes the closure of KCNA1, KCNA2 and KCNA5 channels (PubMed:
7499366, PubMed:
7890032, PubMed:
7603988, PubMed:
7649300, PubMed:
8938711, PubMed:
12077175, PubMed:
12130714, PubMed:
15361858, PubMed:
17540341, PubMed:
19713757). Accelerates KCNA4 channel closure (PubMed:
7890032, PubMed:
7649300, PubMed:
7890764, PubMed:
9763623). Accelerates the closure of heteromeric channels formed by KCNA1 and KCNA4 (PubMed:
17156368). Accelerates the closure of heteromeric channels formed by KCNA2, KCNA5 and KCNA6 (By similarity). Isoform KvB1.2 has no effect on KCNA1, KCNA2 or KCNB1 (PubMed:
7890032, PubMed:
7890764). Enhances KCNB1 and KCNB2 channel activity (By similarity). Binds NADPH; this is required for efficient down-regulation of potassium channel activity (PubMed:
17540341). Has NADPH-dependent aldoketoreductase activity (By similarity). Oxidation of the bound NADPH strongly decreases N-type inactivation of potassium channel activity (By similarity).