Importantly, the mutations R1441C/G in the GTPase domain and Y1699C in the adjacent COR domain, significantly decrease GTPase activity (Figure 2G) although the mutations, G2019S and I2020T, in the kinase domain do not have a significant effect, suggesting that impaired GTP hydrolysis of LRRK2 can contribute to PD. Here, LRRK2 is linked to Parkinson disease.