Regulatory subunit of casein kinase II/CK2. As part of the kinase complex regulates the basal catalytic activity of the alpha subunit a constitutively active serine/threonine-protein kinase that phosphorylates a large number of substrates containing acidic residues C-terminal to the phosphorylated serine or threonine (PubMed:11239457, PubMed:16818610). Participates in Wnt signaling (By similarity). Casein kinase II/CK2 is a tetramer composed of an alpha subunit, an alpha' subunit and two beta subunits. The beta subunit dimerization is mediated by zinc ions. Interacts with DYNLT2 (By similarity). Interacts with CD163. Also a component of a CK2-SPT16-SSRP1 complex composed of SSRP1, SUPT16H, CSNK2A1, CSNK2A2 and CSNK2B, the complex associating following UV irradiation. Interacts with MUSK; mediates phosphorylation of MUSK by CK2. Interacts with FGF1; this interaction is increased in the presence of FIBP, suggesting a possible cooperative interaction between CSNKB and FIBP in binding to FGF1. Phosphorylated by alpha subunit. The disease is caused by variants affecting the gene represented in this entry. Belongs to the casein kinase 2 subunit beta family.