The Molecular Basis for Phosphodependent Substrate Targeting and Regulation of Plks by the Polo-Box Domain

• Published in: Cell Vol. 115; no. 1; pp. 83 - 95
• Main Authors: 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.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 03.10.2003
• Subjects: Amino Acid Motifs; Amino Acid Sequence; Animals; Binding Sites; Cell Cycle Proteins; Crystallography, X-Ray; Fungal Proteins - genetics; Fungal Proteins - metabolism; HeLa Cells; Humans; Models, Molecular; Molecular Sequence Data; Molecular Structure; Mutation; Phosphopeptides - chemistry; Phosphopeptides - metabolism; Polo-Like Kinase 1; Protein Binding; Protein Conformation; Protein Kinases - chemistry; Protein Kinases - genetics; Protein Kinases - metabolism; Protein Serine-Threonine Kinases - chemistry; Protein Serine-Threonine Kinases - genetics; Protein Serine-Threonine Kinases - metabolism; Protein Structure, Tertiary; Proto-Oncogene Proteins; Sequence Alignment; Substrate Specificity; Xenopus
• ISSN: 0092-8674; 1097-4172
• 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 Å X-ray structure of a human Plk1 PBD-phosphopeptide complex shows that the Polo boxes each comprise β 6α structures that associate to form a 12-stranded β 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.