Introduction Plants and TOR

Target of rapamycin (TOR) proteins are large, highly conserved protein kinases encoded in almost every eukaryotic genome. All TOR proteins identified, from the basal eukaryote Giardia lamblia (Morrison et al. 2002) to yeast (Heitman et al. 1991) and metazoans (Chen et al. 1995), share the same set of structural motifs (Schmelzle and Hall 2000). The first ~1800 residues include a set of ~14 N-terminal HEAT repeats (Kunz et al. 2000), a DNA binding domain, a nuclear export signal, and a nuclear import signal (Li et al. 2006). The final 600 residues contain the rapamycin-binding domain (Chen et al. 1995), the kinase domain, and both halves of the split FAT domain (Bosotti et al. 2000). TOR proteins show sequence similarity to Phoshpatidyl-inositol 3-like kinases (PI3K) but are Ser/Thr protein kinases. HEAT repeats and FAT domains mediate protein-protein interactions, suggesting that TOR has the potential to interact with multiple binding partners.

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