Download MendeleyThe Immunity-Related Gtpase Irga6 Dimerizes in a Parallel Head-to-Head Fashion.
Schulte, K., Pawlowski, N., Faelber, K., Froehlich, C., Howard, J., Daumke, O.(2016) BMC Biol 14: 14
- PubMed: 26934976
- DOI: https://doi.org/10.1186/s12915-016-0236-7
- Primary Citation of Related Structures:
5FPH - PubMed Abstract:
The immunity-related GTPases (IRGs) constitute a powerful cell-autonomous resistance system against several intracellular pathogens. Irga6 is a dynamin-like protein that oligomerizes at the parasitophorous vacuolar membrane (PVM) of Toxoplasma gondii leading to its vesiculation. Based on a previous biochemical analysis, it has been proposed that the GTPase domains of Irga6 dimerize in an antiparallel fashion during oligomerization. We determined the crystal structure of an oligomerization-impaired Irga6 mutant bound to a non-hydrolyzable GTP analog. Contrary to the previous model, the structure shows that the GTPase domains dimerize in a parallel fashion. The nucleotides in the center of the interface participate in dimerization by forming symmetric contacts with each other and with the switch I region of the opposing Irga6 molecule. The latter contact appears to activate GTP hydrolysis by stabilizing the position of the catalytic glutamate 106 in switch I close to the active site. Further dimerization contacts involve switch II, the G4 helix and the trans stabilizing loop. The Irga6 structure features a parallel GTPase domain dimer, which appears to be a unifying feature of all dynamin and septin superfamily members. This study contributes important insights into the assembly and catalytic mechanisms of IRG proteins as prerequisite to understand their anti-microbial action.
Organizational Affiliation:
Max-Delbrueck-Centrum for Molecular Medicine, Crystallography, Robert-Rössle-Strasse 10, 13125, Berlin, Germany.
