| Category | Key points | Key evidence & notes | Primary sources (with year, DOI URL) |
|---|---|---|---|
| Molecular function | TOR1 encodes a large PI3/PI4-kinase-family, atypical serine/threonine protein kinase; its C-terminal kinase region is the catalytically relevant domain. | TOR1/TOR2 are described as phosphatidylinositol-kinase homologs/PIKK-family proteins with HEAT, FAT/FATC and FRB regions; current understanding is that the biologically relevant activity is Ser/Thr protein kinase activity rather than lipid kinase activity (pqac-00000000, pqac-00000001, pqac-00000007). | Emmerstorfer-Augustin & Thorner 2023, https://doi.org/10.1146/annurev-cellbio-011723-030346; Wang et al. 2023, https://doi.org/10.3390/microorganisms11010218; Schmelzle & Hall 2000, https://doi.org/10.1016/S0092-8674(00)00117-3 |
| Complex membership | In budding yeast, TOR1 is the primary catalytic subunit of TORC1; TORC1 can contain Tor1 or Tor2, whereas TORC2 contains Tor2 exclusively. TORC1 is rapamycin-sensitive. | Genetic evidence summarized in review: tor1Δ is viable, tor2Δ is lethal; TORC1 function can be supported by either Tor1 or Tor2, but TORC2 requires Tor2. Reviews describe TORC1 core composition as Tor1/Tor2 with Kog1 and Lst8, and TORC1 is the rapamycin-sensitive complex (pqac-00000000, pqac-00000001). | Emmerstorfer-Augustin & Thorner 2023, https://doi.org/10.1146/annurev-cellbio-011723-030346; Wang et al. 2023, https://doi.org/10.3390/microorganisms11010218 |
| Localization | TOR1-containing TORC1 localizes to the vacuolar membrane/cytosolic vacuole surface; upon glucose depletion, TORC1 redistributes into vacuolar puncta/condensates called TOROIDs. | 2023 review places TORC1 at the vacuolar membrane through Rag GTPases/EGO machinery. 2023 structural study shows glucose depletion or post-diauxic shift promotes TOROID formation; EGOC colocalizes with TORC1 puncta. Figure-level evidence identifies TOROID structural organization and redistribution from vacuole surface into puncta (pqac-00000001, pqac-00000002, pqac-00000005, pqac-00000008). | Wang et al. 2023, https://doi.org/10.3390/microorganisms11010218; Prouteau et al. 2023, https://doi.org/10.1038/s41594-022-00912-6 |
| Regulation | TOR1/TORC1 is activated mainly by nutrient cues, especially amino acids, through Gtr1-Gtr2 Rag-family GTPases and the EGO complex; Vam6, SEAC complexes, Lst4-Lst7, Pib2, phosphate signals, AMPK/stress inputs and glucose availability modulate activity. | Active Gtr1-GTP/Gtr2-GDP promotes TORC1; inactive Gtr1-GDP/Gtr2-GTP inhibits it. Vam6 acts as GEF for Gtr1; SEAC complexes tune Rag-state signaling; Lst4-Lst7 promotes the activating Gtr1-GTP/Gtr2-GDP state via Gtr2 GAP activity; Pib2 is a vacuolar TORC1-localized regulator. Glucose depletion promotes inactive TOROID assembly, while active EGOC antagonizes TOROID formation (pqac-00000001, pqac-00000002, pqac-00000004, pqac-00000005). | Wang et al. 2023, https://doi.org/10.3390/microorganisms11010218; Prouteau et al. 2023, https://doi.org/10.1038/s41594-022-00912-6 |
| Downstream processes | TOR1/TORC1 promotes protein synthesis, translation initiation and ribosome biogenesis, and suppresses autophagy under nutrient-rich conditions. | Reviews and classic studies agree that TOR signaling supports translation and ribosome biogenesis through Sch9 and Tap42 branches; downstream factors include Gcn2/eIF2α, Maf1, Ifh1, Stb3, Dot6, Tod6. Rapamycin or TOR loss causes severe reduction in protein synthesis; TOR inhibition induces autophagy and starvation-like transcriptional responses (pqac-00000004, pqac-00000006, pqac-00000007). | Wang et al. 2023, https://doi.org/10.3390/microorganisms11010218; Schmidt et al. 1998, https://doi.org/10.1093/emboj/17.23.6924; Schmelzle & Hall 2000, https://doi.org/10.1016/S0092-8674(00)00117-3 |
| Substrate-linked pathway evidence | TOR signaling phosphorylates/controls pathway effectors including Npr1 and Tap42-associated phosphatase signaling, linking nutrient status to permease turnover and translation control. | In a primary 1998 study, TOR pathway activity phosphorylates the Ser/Thr kinase Npr1; loss of TOR signaling leads to rapid Npr1 dephosphorylation and starvation-induced turnover of the tryptophan permease Tat2. TOR also promotes association of PP2A-related phosphatases with Tap42, supporting translation initiation (pqac-00000006). | Schmidt et al. 1998, https://doi.org/10.1093/emboj/17.23.6924 |
| Phenotypes | Reduced TOR1/TORC1 signaling causes early G1/G0 arrest, severe reduction in protein synthesis, glycogen accumulation, thermotolerance, vacuole enlargement, autophagy induction, and starvation-like transcriptional reprogramming. | These phenotypes were observed after rapamycin treatment or combined TOR1/TOR2 pathway loss in classic studies; TORC1 also contributes to cell size and broader growth/stress programs in reviews (pqac-00000001, pqac-00000006, pqac-00000007). | Wang et al. 2023, https://doi.org/10.3390/microorganisms11010218; Schmidt et al. 1998, https://doi.org/10.1093/emboj/17.23.6924; Schmelzle & Hall 2000, https://doi.org/10.1016/S0092-8674(00)00117-3 |
| Rapamycin resistance mutations | Dominant rapamycin-resistant TOR1 alleles map to the FRB domain, notably substitutions at Ser1972, which disrupt FKBP12-rapamycin binding. | Review evidence states rapamycin acts through FKBP12/Fpr1; fpr1Δ is completely resistant. Dominant TOR1 resistance alleles alter Ser1972 to Arg or Asn, pinpointing the FRB domain as the binding interface for FKBP-rapamycin (pqac-00000000). | Emmerstorfer-Augustin & Thorner 2023, https://doi.org/10.1146/annurev-cellbio-011723-030346 |
| Recent structural insights | 2023 cryo-EM resolved yeast TORC1 within TOROIDs at 3.9 Å and showed EGOC binding structurally opposes TOROID polymerization, favoring active TORC1. | Prouteau et al. reconstructed TORC1 from TOROIDs and reported stronger intracoil than intercoil contacts in the TOROID helix. Functional assays quantified TOROID/EGOC puncta by microscopy (n=2 experiments, at least 77 cells per replicate) and pull-downs (n=3); cells were assayed on 2.5 nM rapamycin plates. This provides current mechanistic evidence for nutrient-dependent spatial regulation of TOR1-containing TORC1 (pqac-00000002, pqac-00000008). | Prouteau et al. 2023, https://doi.org/10.1038/s41594-022-00912-6 |


*Table: This table summarizes the experimentally supported functional annotation of Saccharomyces cerevisiae TOR1 (UniProt P35169), emphasizing verified TORC1 membership, vacuolar localization, nutrient regulation, downstream growth/autophagy control, and 2023 structural advances.*