Casein kinase 1 (CK1)

The casein kinase I (CKI) family of serine/threonine protein kinases is highly conserved from yeast to humans. The CKI family is involved in many diverse and important cellular functions, such as regulation of membrane transport, cell division, DNA repair, circadian rhythms, and nuclear localization. The name of the enzyme family was originated from the convenience of casein as a substrate since the earliest days of research on protein phosphorylation. Mammals have seven family members: α, β, γ1, γ2, γ3, δ, and ε. Sometimes they are referred to as isoforms but they are encoded by distinct genes. The family members appear to have similar substrate specificity in vitro and substrate selection is thought to be regulated in vivo via subcellular localization and docking sites in specific substrates. CK1α is the smallest member of the family consisting of only 325 amino acids (37.5 kDa). It can mediate phosphorylation of a wide range of proteins, including many signaling molecules. It has been suggested to play a role in phosphorylation of Disheveled in the Wnt signaling pathway.