Fig. 5. PAR-6 protein localizes to the CAB. (A) Domain structure of PAR-6 proteins. PB1, Phox and Bem protein interaction domain, which binds aPKC protein; CRIB, CDC42 interacting domain; PDZ, protein interaction domain, which binds PAR-3 protein. (B) Comparison of PAR-6 sequences from Phallusia mammillata (Pm), Ciona intestinalis (Ci), Caenorhabditis elegans (Ce), Drosophila melanogaster (Dm), Xenopus laevis (Xl) and Mus musculus (Mm). Boxed areas indicate N-terminal (MDKTSSGQRAPSP) and C-terminal (RDVSVKAKRSNEPQD) peptides used to raise antibodies. (C) A single 45 kDa band is detected on a western blot of Phallusia egg extract using sera purified against the synthetic peptide (lane 1) or against the PAR-6 fusion protein (lane 2). (D,E) Both PAR-6 antibodies directed against either the N-terminal or C-terminal peptides label the surface of posterior vegetal blastomeres at the position of the CABs (arrowheads).