Cytoplasmic potassium channel subunit that modulates the characteristics of the channel-forming alpha-subunits (PubMed:9763623, PubMed:21357749). Contributes to the regulation of nerve signaling, and prevents neuronal hyperexcitability (By similarity). Promotes expression of the pore-forming alpha subunits at the cell membrane, and thereby increases channel activity (PubMed:10896669, PubMed:16770729, PubMed:18003609, PubMed:21357749). Promotes potassium channel closure via a mechanism that does not involve physical obstruction of the channel pore (PubMed:21357749). Modulates the functional properties of KCNA4 (PubMed:9763623). Modulates the functional properties of KCNA5 (By similarity). Enhances KCNB2 channel activity (By similarity). Binds NADPH and has NADPH-dependent aldoketoreductase activity (PubMed:18672894, PubMed:21209188). Has broad substrate specificity and can catalyze the reduction of methylglyoxal, 9,10-phenanthrenequinone, prostaglandin J2, 4-nitrobenzaldehyde, 4-nitroacetophenone and 4-oxo-trans-2-nonenal (in vitro) (PubMed:18672894). Optimum pH is 7.2-7.4. Homotetramer (PubMed:10884227, PubMed:16002581, PubMed:18004376, PubMed:18806782, PubMed:20534430, PubMed:20360102, PubMed:23705070). Interaction with tetrameric potassium channel alpha subunits gives rise to a heterooctamer (PubMed:10884227, PubMed:16002581, PubMed:18004376, PubMed:18806782, PubMed:20534430, PubMed:20360102, PubMed:23705070). Identified in potassium channel complexes containing KCNA1, KCNA2, KCNA4, KCNA5, KCNA6, KCNAB1 and KCNAB2 (PubMed:9334400). Interacts with KCNA1 (PubMed:23318870, PubMed:10884227). Interacts with KCNA2 (PubMed:18003609, PubMed:21357749, PubMed:23318870, PubMed:16002581, PubMed:18004376, PubMed:18806782, PubMed:20534430, PubMed:20360102, PubMed:23705070). Interacts with KCNA4 and KCND3 (PubMed:12860406). Interacts with KCNA5 (By similarity). Interacts with KCNB2 (By similarity). Interacts (in unphosphorylated form) with MAPRE1 (PubMed:21357749). Forms a ternary complex with SQSTM1 and PRKCZ (PubMed:10477520). Recruited to the cytoplasmic side of the cell membrane via its interaction with pore-forming potassium channel alpha subunits. Associates with microtubules when unphosphorylated (PubMed:21357749). Detected in brain (PubMed:9334400, PubMed:21357749). Detected in the middle third of the molecular layer of the dentate gyrus in hippocampus (PubMed:9334400). Detected in neurons in the deep cerebellar nucleus (PubMed:23318870). Detected in globus pallidus and pars reticulata of the substantia nigra (PubMed:9334400). Detected in cerebellum (PubMed:23318870). Detected at axon terminal plexuses of cerebellar granule cells (PubMed:9334400). Detected in the juxtaparanodal region of nodes of Ranvier in cerebellum (at protein level) (PubMed:9334400). Detected in mesenteric arteries (PubMed:15618540). In contrast to KCNAB1, the shorter N-terminal domain of KCNAB2 cannot mediate closure of delayed rectifier potassium channels by physically obstructing the pore. Phosphorylated by PRKCZ; may be regulated by incorporation in a complex composed of PRKCZ and SQSTM1. Belongs to the shaker potassium channel beta subunit family.