Enables protein serine/threonine kinase activity. Involved in several processes, including lateral inhibition; locomotor rhythm; and positive regulation of smoothened signaling pathway. Located in cytosol and nucleus. Part of protein kinase CK2 complex. Is expressed in adult head; adult heart; adult s-LNv neurons; and spermatozoon. Orthologous to several human genes including CSNK2A1 (casein kinase 2 alpha 1) and CSNK2A3 (casein kinase 2 alpha 3).