This Polo box (PB) domain is found in Polo-like kinase 4 (Plk4) present in Drosophila melanogaster. Plk4 is a conserved component in the duplication pathway of centrioles which is needed to prevent chromosomal instability. Plk4 localizes to centrioles in M/G1. Structural analysis reveals two tandem, homodimerized polo boxes, PB1-PB2, that form a winged architecture. This domain is PB2, together with PB1 Pfam:PF18190 , they are required for binding the centriolar protein Asterless (Asl) as well as robust centriole targeting. In other words, PB1-PB2 cassette collectively binds Asl and affords robust centriole localization, optimally positioning the kinase domain for trans-autophosphorylation [1].

1: The structure of the plk4 cryptic polo box reveals two tandem polo boxes required for centriole duplication. Slevin LK, Nye J, Pinkerton DC, Buster DW, Rogers GC, Slep KC; Structure. 2012;20:1905-1917. PMID:23000383

2: Structure of the C. elegans ZYG-1 cryptic polo box suggests a conserved mechanism for centriolar docking of Plk4 kinases. Shimanovskaya E, Viscardi V, Lesigang J, Lettman MM, Qiao R, Svergun DI, Round A, Oegema K, Dong G; Structure. 2014;22:1090-1104. PMID:24980795

3: Molecular basis for unidirectional scaffold switching of human Plk4 in centriole biogenesis. Park SY, Park JE, Kim TS, Kim JH, Kwak MJ, Ku B, Tian L, Murugan RN, Ahn M, Komiya S, Hojo H, Kim NH, Kim BY, Bang JK, Erikson RL, Lee KW, Kim SJ, Oh BH, Yang W, Lee KS; Nat Struct Mol Biol. 2014;21:696-703. PMID:24997597