| Primary Identifier | IPR046437 | Type | Homologous_superfamily |
| Short Name | Ser_Thr-PK_POLO_box_1_sf |
| description | The polo-like Ser/Thr kinases (Plk1, Plk2/Snk, Plk3/Prk/Fnk, Plk4/Sak, and the inactive kinase Plk5) play various roles in cytokinesis and mitosis. At their C terminus, they contain a tandemly repeated polo-box domain (PBD) (in the case of Plk4, a tandem repeat of cryptic PBDs is found in the middle of the protein followed by a C-terminal single repeat), which appears to be involved in autoinhibition and in mediating the subcellular localization. The latter may be controlled via interactions between the polo-box domain and phospho-peptide motifs. The phosphopeptide binding site is formed at the interface between the two tandemly repeated PBDs. The PBDs of Plk4/Sak appear unique in participating in homodimer interactions, though it is not clear whether and how they interact with phosphopeptides [, , , , , ].In metazoans, Plk4 kinases control daughter centriole assembly. Plk4 homologues have an N-terminal kinase domain, a C-terminal polo box, and a central domain termed the 'cryptic polo box' (CPB) that has been shown to dimerize, to be sufficient for centriole localization and to be required for Plk4 to promote centriole assembly. Probable serine/threonine-protein kinase zyg-1 () (ZYG-1) is a Plk4 homologue found in C. elegans. Crystal structure for the CPB of C. elegans ZYG-1, reveals that it forms a Z-shaped dimer containing an intermolecular β-sheet with an extended basic surface patch. Electrostatic interactions between the basic patch on the ZYG-1 CPB dimer and the SPD-2 acidic region dock ZYG-1 onto centrioles to promote new centriole assembly. ZYG-1 CPB contains two tandem polo boxes (PB1 and PB2), each containing a six-stranded β-sheet with an α-helix packed against one side [].This entry represents the first (cryptic) polo-box domain of Plk4 and homologues. |
