The casein kinases (CK) belong to the serine/threonine kinases and can be subdivided further into either casein kinase 1 (CK1) or casein kinase 2 (CK2) families due to their high homology in their catalytic domains.In vertebrates, seven CK1 isoforms (α, β, γ1, γ2, γ3, δ and ϵ) and several splice variants for CK1α, δ, ϵ and γ3 have been identified. They differ in length and sequence of the N-terminal (9–76 amino acids) and especially the C-terminal (24–200 amino acids) non-catalytic domain.
