Structure and regulation of full-length human leucine-rich repeat kinase 1

The two human leucine-rich repeat kinases (LRRKs), LRRK1 and LRRK2 are large and unusually complex multi-domain kinases which serve to regulate fundamental cellular processes, with both implicated in human disease. Despite recent experimentally determined structures of LRRK2, the structure and exact molecular mechanisms regulating the activity of the LRRK1, and differences in the regulation of LRRK1 and LRRK2 remain unclear. Here, we report a cryo-EM structure of the LRRK1 monomer, and a lower-resolution cryo-EM map of the LRRK1 dimer. The monomer structure, in which the kinase is in an inactive conformation, reveals key interdomain interfaces which serve to control kinase activity, which are further validated experimentally. Both the LRRK1 monomer and dimer are structurally distinct compared to LRRK2, implying functional differences in both proteins. Overall, our results provide new structural insights into the activation of the human LRRKs for understanding the physiology and pathology of these proteins. ### Competing Interest Statement The authors have declared no competing interest.