Back

Structural basis of Irgb6 inactivation by Toxoplasma gondii through the phosphorylation of switch I.

Okuma, H.; Saijo-Hamano, Y.; Sherif, A. A.; Hoshizaki, E.; Sakai, N.; Kato, T.; Imasaki, T.; Nitta, E.; Sasai, M.; Maniwa, Y.; Kosako, H.; Standley, D. M.; Yamamoto, M.; Nitta, R.

2022-11-01 microbiology
10.1101/2022.10.31.514472 bioRxiv
Show abstract

Upon infection with Toxoplasma gondii, host cells produce immune-related GTPases (IRGs) to kill the parasite. T. gondii counters this response by releasing ROP18 kinase, which inactivates IRG GTPases and inhibits their recruitment to the T. gondii parasitophorous vacuole (PV). However, the molecular mechanisms of this process are entirely unknown. Here we report the atomic structures of Irgb6 with a phosphomimetic mutation by ROP18. The mutant has lower GTPase activity and is not recruited to the PV membrane (PVM). The crystal structure shows the mutant exhibit a distinct conformation from the physiological nucleotide-free form, thus preventing GTPase cycling. This change allosterically modifies the conformation of the membrane-binding interface, preventing physiological PVM-binding. Docking simulation of PI5P also supports the impaired binding of the mutant to PVM. We thus demonstrate the structural basis for T. gondii escape from host cell-autonomous defense, and provide a structural model for regulating enzymatic activity by phosphorylation.

Matching journals

The top 7 journals account for 50% of the predicted probability mass.

50% of probability mass above

"Similar papers" are the closest papers from that journal in the model's embedding space. They show what the match is built on, but the ranking comes mostly from a classifier over the whole training set, not from these examples alone.