Elia Andrew E H, Rellos Peter, Haire Lesley F, Chao Jerry W, Ivins Frank J, Hoepker Katja, Mohammad Duaa, Cantley Lewis C, Smerdon Stephen J, Yaffe Michael B
Center for Cancer Research, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Cell. 2003 Oct 3;115(1):83-95. doi: 10.1016/s0092-8674(03)00725-6.
Polo-like kinases (Plks) perform crucial functions in cell-cycle progression and multiple stages of mitosis. Plks are characterized by a C-terminal noncatalytic region containing two tandem Polo boxes, termed the Polo-box domain (PBD), which has recently been implicated in phosphodependent substrate targeting. We show that the PBDs of human, Xenopus, and yeast Plks all recognize similar phosphoserine/threonine-containing motifs. The 1.9 A X-ray structure of a human Plk1 PBD-phosphopeptide complex shows that the Polo boxes each comprise beta6alpha structures that associate to form a 12-stranded beta sandwich domain. The phosphopeptide binds along a conserved, positively charged cleft located at the edge of the Polo-box interface. Mutations that specifically disrupt phosphodependent interactions abolish cell-cycle-dependent localization and provide compelling phenotypic evidence that PBD-phospholigand binding is necessary for proper mitotic progression. In addition, phosphopeptide binding to the PBD stimulates kinase activity in full-length Plk1, suggesting a conformational switching mechanism for Plk regulation and a dual functionality for the PBD.
Polo样激酶（Plks）在细胞周期进程和有丝分裂的多个阶段发挥关键作用。Plks的特征是其C末端非催化区域包含两个串联的Polo框，称为Polo框结构域（PBD），最近发现该结构域与磷酸依赖性底物靶向有关。我们发现，人类、非洲爪蟾和酵母的Plks的PBD均识别相似的含磷酸丝氨酸/苏氨酸基序。人Plk1 PBD-磷酸肽复合物的1.9埃X射线结构表明，每个Polo框均由β6α结构组成，这些结构相互关联形成一个12链β折叠夹心结构域。磷酸肽沿着位于Polo框界面边缘的保守正电荷裂隙结合。特异性破坏磷酸依赖性相互作用的突变消除了细胞周期依赖性定位，并提供了令人信服的表型证据，表明PBD-磷酸配体结合对于正确的有丝分裂进程是必需的。此外，磷酸肽与PBD的结合刺激全长Plk1的激酶活性，提示Plk调节的构象转换机制以及PBD的双重功能。
