title: Molecular details of the Raptor-binding motif on Arabidopsis S6 kinase.
abstract: A putative raptor-binding fragment was identified from Arabidopsis S6 kinase 1 (AtS6K1) N-terminal domain in our previous study. Here, we report a further characterization of this fragment, which identified a 12-amino acid core element absolutely required for the interaction. Although the amino acid sequence of the element per se had no significant homology with the canonical consensus of the TOS (TOR-signaling) motif found in the mammalian TOR (target of rapamycin) kinase substrates, its overall sequence composition is similar to that of the TOS motif in that the acidic and non-polar amino acids residues are arranged in alternating fashion and having one or two of the bulky hydrophobic amino acid (F) buried in the interior. Substitution of this bulky residue completely abolished the binding of the fragment to AtRaptor1, as in the case of the mammalian TOS motif. Taken together with its position relative to the catalytic domain of the kinase, which also shows a resemblance with the TOS motif, these results appear to suggest that this core binding element in the N-terminus of AtS6K1 represents a plant version of the TOS motif.
authors.affiliation: Department of Biological Science, Sookmyung Women's University, Seoul 140-742, South Korea.
authors.forename: Ora
authors.initials: O
authors.lastname: Son
authors.affiliation: Department of Biological Science, Sookmyung Women's University, Seoul 140-742, South Korea.
authors.forename: Sunghan
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Biological Science, Sookmyung Women's University, Seoul 140-742, South Korea.
authors.forename: Yoon-Sun
authors.initials: YS
authors.lastname: Hur
authors.affiliation: Department of Biological Science, Sookmyung Women's University, Seoul 140-742, South Korea. Electronic address: ccheon@sookmyung.ac.kr.
authors.forename: Choong-Ill
authors.initials: CI
authors.lastname: Cheon
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019893:Ribosomal Protein S6 Kinases / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; C496442:Raptor1 protein, Arabidopsis; D019869:Phosphatidylinositol 3-Kinases; C512171:TOR protein, Arabidopsis; D019893:Ribosomal Protein S6 Kinases
keywords: Arabidopsis ribosomal S6 kinase 1; AtRaptor1; TOR; rDNA transcription