Ullah Hemayet, Scappini Erica Louise, Moon Andrea Florence, Williams Latanya Veronica, Armstrong David Lee, Pedersen Lars Christian
Department of Biology, Howard University, Washington, DC 20059, USA.
Protein Sci. 2008 Oct;17(10):1771-80. doi: 10.1110/ps.035121.108. Epub 2008 Aug 20.
The receptor for activated C-kinase 1 (RACK1) is a highly conserved WD40 repeat scaffold protein found in a wide range of eukaryotic species from Chlamydymonas to plants and humans. In tissues of higher mammals, RACK1 is ubiquitously expressed and has been implicated in diverse signaling pathways involving neuropathology, cellular stress, protein translation, and developmental processes. RACK1 has established itself as a scaffold protein through physical interaction with a myriad of signaling proteins ranging from kinases, phosphatases, ion channels, membrane receptors, G proteins, IP3 receptor, and with widely conserved structural proteins associated with the ribosome. In the plant Arabidopsis thaliana, RACK1A is implicated in diverse developmental and environmental stress pathways. Despite the functional conservation of RACK1-mediated protein-protein interaction-regulated signaling modes, the structural basis of such interactions is largely unknown. Here we present the first crystal structure of a RACK1 protein, RACK1 isoform A from Arabidopsis thaliana, at 2.4 A resolution, as a C-terminal fusion of the maltose binding protein. The structure implicates highly conserved surface residues that could play critical roles in protein-protein interactions and reveals the surface location of proposed post-transcriptionally modified residues. The availability of this structure provides a structural basis for dissecting RACK1-mediated cellular signaling mechanisms in both plants and animals.
活化C激酶1受体（RACK1）是一种高度保守的WD40重复支架蛋白，存在于从衣藻到植物和人类等广泛的真核生物物种中。在高等哺乳动物的组织中，RACK1广泛表达，并参与了涉及神经病理学、细胞应激、蛋白质翻译和发育过程的多种信号通路。RACK1通过与多种信号蛋白进行物理相互作用，确立了其作为支架蛋白的地位，这些信号蛋白包括激酶、磷酸酶、离子通道、膜受体、G蛋白、IP3受体，以及与核糖体相关的广泛保守的结构蛋白。在植物拟南芥中，RACK1A参与了多种发育和环境应激途径。尽管RACK1介导的蛋白质-蛋白质相互作用调节的信号传导模式在功能上具有保守性，但这种相互作用的结构基础在很大程度上尚不清楚。在此，我们展示了拟南芥RACK1蛋白异构体A的首个晶体结构，分辨率为2.4埃，它是麦芽糖结合蛋白的C末端融合体。该结构表明高度保守的表面残基可能在蛋白质-蛋白质相互作用中起关键作用，并揭示了转录后修饰残基的表面位置。该结构的获得为剖析植物和动物中RACK1介导的细胞信号传导机制提供了结构基础。
