TOR Complex Homologues

A clear TOR homologue, AtTOR (At1g50030), has been identified in Arabidopsis (Menand et al. 2002). TOR homologues are easily recognized in all plants with sufficient sequence information. All share the TOR motifs described above.

Arabidopsis encodes two LSTS/G^l homologues (At3g18140, At2g22040). Like LST8 and mammalian Gfil, both Arabidopsis LST8 proteins are comprised of seven WD-40 repeats. WD-40 repeats, like the HEAT repeats and the split FAT domain in TOR, mediate protein-protein interactions.

The TORCl-specific protein Raptor/KOGl is encoded in two copies in Arabidopsis, AtRaptorlA (At5g01770) and AtRaptorlB (At3g08850)—also called Raptor2 and Raptorl, respectively (Anderson et al. 2005; Deprost et al. 2005). Both AtRaptor loci encode proteins comprised of an RNC (Raptor N-terminal Conserved) domain, three HEAT repeats and seven WD-40 repeats, as is common for all Raptor proteins (Shinozaki-Yabana et al. 2000). The RNC domain shows some similarity to a protease domain (Ginalski et al. 2004) but has not been shown to harbor catalytic activity.

The TORC2-specific proteins Rictor/AVO3 and hSinl/AVOl are not found in any available plant sequence. Indeed, Rictor and hSinl homologues are found only in the genomes of fungi, metazoans, slime molds, and ciliates.

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