Cytoplasmic potassium channel subunit that modulates the characteristics of the channel-forming alpha-subunits (By similarity). 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 (By similarity). Promotes potassium channel closure via a mechanism that does not involve physical obstruction of the channel pore (By similarity). Promotes KCNA4 channel closure (By similarity). Modulates the functional properties of KCNA5 (By similarity). Enhances KCNB2 channel activity (By similarity). Binds NADPH and has NADPH-dependent aldoketoreductase activity (By similarity). 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) (By similarity). Homotetramer (By similarity). Interaction with tetrameric potassium channel alpha subunits gives rise to a heterooctamer (By similarity). Identified in potassium channel complexes containing KCNA1, KCNA2, KCNA4, KCNA5, KCNA6, KCNAB1 and KCNAB2 (By similarity). Interacts with KCNA1 (PubMed:11086297). Interacts with KCNA2 (PubMed:11086297). Interacts with KCNA4 and KCND3 (By similarity). Interacts with KCNA5 (By similarity). Interacts with KCNB2 (By similarity). Interacts (in unphosphorylated form) with MAPRE1 (By similarity). Forms a ternary complex with SQSTM1 and PRKCZ (By similarity). Recruited to the cytoplasmic side of the cell membrane via its interaction with pore-forming potassium channel alpha subunits. Associates with microtubules when unphosphorylated. Detected in the juxtaparanodal region of nodes of Ranvier in myelinated nerve fibers in the spinal cord (at protein level). 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.