Son Ora, Kim Sunghan, Hur Yoon-Sun, Cheon Choong-Ill
Department of Biological Science, Sookmyung Women's University, Seoul 140-742, South Korea.
Department of Biological Science, Sookmyung Women's University, Seoul 140-742, South Korea.
Biochem Biophys Res Commun. 2017 Apr 22;486(1):137-142. doi: 10.1016/j.bbrc.2017.03.013. Epub 2017 Mar 8.
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.
在我们之前的研究中，从拟南芥S6激酶1（AtS6K1）的N端结构域中鉴定出一个假定的与AtRaptor结合的片段。在此，我们报道了对该片段的进一步表征，确定了一个对于相互作用绝对必需的12个氨基酸的核心元件。尽管该元件本身的氨基酸序列与在哺乳动物雷帕霉素靶蛋白（TOR）激酶底物中发现的TOR信号（TOS）基序的典型共有序列没有显著同源性，但其整体序列组成与TOS基序相似，因为酸性和非极性氨基酸残基以交替方式排列，并且有一个或两个大的疏水氨基酸（F）埋在内部。与哺乳动物TOS基序的情况一样，这个大的残基的取代完全消除了该片段与AtRaptor1的结合。连同其相对于激酶催化结构域的位置（这也与TOS基序相似），这些结果似乎表明AtS6K1 N端的这个核心结合元件代表了TOS基序的植物版本。
