The N-terminal GTPase of Miro1 regulates oligomer formation

The outer-mitochondrial membrane protein Miro1 is critical for the regulation of mitochondrial trafficking. Miro1 contains two GTPase domains, where changes in the N-terminal GTPase nucleotide state strongly affects mitochondrial trafficking. Previous work showed that the GTP-locked mutation Miro1P13V decreases trafficking and affects mitochondrial dynamics. Despite showing a clear role in Miro1 function, the molecular basis for this activity remains unknown. Using in vitro reconstitution, we demonstrate that Miro1 self-associates to form dimers and higher-ordered species. Structural characterization of Miro1P13V suggests that the oligomers adopt a range of conformations in vitro. Additionally, Miro1P13V has diminished interaction with its downstream cargo adapter TRAK1. These results indicate that the NGTPase of Miro1 facilitates the formation of higher-ordered species and suggests that changes in the oligomeric state may regulate mitochondrial trafficking through reduced association with TRAK1.