The phosphorylation and dephosphorylation of proteins on serine and threonine residues is an essential means of regulating a broad range of cellular functions in eukaryotes, including cell division, homeostasis and apoptosis. å-protein kinase 2, also known as ALPK2 or HAK (Heart alpha-protein kinase), is a 2,170 amino acid member of the protein kinase superfamily and contains one å-type protein kinase domain and one Ig-like domain. Expressed at higher levels in heart tissue, å-protein kinase 2 recognizes and phosphorylates specific phosphorylation sites that are surrounded by peptides which have an å-helical conformation, possibly playing a role in vesicle trafficking.