LRRK2 is a multidomain protein that includes a kinase domain, a GTPase domain, and a leucine-rich repeat (LRR) domain. Certain mutations (e.g. I2020T, G2019S, and R1441C) in this gene have been associated with Parkinson's disease. D1994A is an artificial mutation that renders the kinase catalytically inactive and thus serves as a useful control for activity assays, especially when testing novel substrates.