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. A group of proteins that are intimately involved in this process are the serine/threonine (Ser/Thr) protein kinases. LRRK1 (leucine-rich repeat serine/threonine-protein kinase 1), also known as RIPK6, Roco1 or KIAA1790, is a 2,038 amino acid cytoplasmic protein that contains one protein kinase domain, four ANK repeats and 11 leucine-rich repeats and belongs to the Ser/Thr protein kinase family. Using magnesium as a cofactor, LRRK1 catalyzes the ATP-dependent phosphorylation of target proteins. The gene encoding LRRK1, which is expressed as four alternatively spliced isoforms, is thought to be involved in the pathogenesis of Parkinson's disease.