Cryo-EM structure of yeast TORC2 reveals its overall architecture and rapamycin insensitivity.
| Evidence tier | D Mechanistic / in vitro / review |
| Study type | 5 - Mechanistic / In Vitro |
| Model system | Cryo-EM structure |
| Journal | Nature communications |
| Year | 2017 |
| Peer reviewed | Yes |
| Source | DOI 10.1038/s41467-017-01862-0 · PMID 29170376 · Free full text (PMC5700991) |
The target of rapamycin (TOR) kinase assembles into two distinct multiprotein complexes, conserved across eukaryote evolution. In contrast to TOR complex 1 (TORC1), TORC2 kinase activity is not inhibited by the macrolide rapamycin. Here, we present the structure of Saccharomyces cerevisiae TORC2 determined by electron cryo-microscopy. TORC2 contains six subunits assembling into a 1.4 MDa rhombohedron. Tor2 and Lst8 form the common core of both TOR complexes. Avo3/Rictor is unique to TORC2, but interacts with the same HEAT repeats of Tor2 that are engaged by Kog1/Raptor in mammalian TORC1, explaining the mutual exclusivity of these two proteins. Density, which we conclude is Avo3, occludes the FKBP12-rapamycin-binding site of Tor2's FRB domain rendering TORC2 rapamycin insensitive and recessing the kinase active site. Although mobile, Avo1/hSin1 further restricts access to the active site as its conserved-region-in-the-middle (CRIM) domain is positioned along an edge of the TORC2 active-site-cleft, consistent with a role for CRIM in substrate recruitment.
| Intervention | Structural (cryo-EM) |
| Target | TORC2 (Tor2/Lst8/Avo) |
| Model | Cryo-EM structure (S. cerevisiae) |
| Effect | Cryo-EM structure of yeast TORC2, a 1.4-MDa rhombohedron of six subunits |