(A–C) Physical interaction of Par3 and Pk3 in transfected HEK293T cells. Myc-Par3 is pulled down from cell lysates with FLAG-Pk3 (A) or FLAG-GFP(FG)-Pk3∆PET (B). FG-Pk3∆PET is pulled down with Myc-Par3 (C). (D, E) Interaction of Par3 and Pk3 in Xenopus embryos assessed by proximity biotinylation. (D) Experimental scheme. Biotin and RNAs encoding FLAG-Biotin Ligase (BL)-Pk3 or FLAG-BL-Vangl2, 0.5 ng each, with or without GFP-Par3 RNA, 0.1 ng, were injected into the animal region of four- to eight- cell embryos. Injected embryos were lysed at stages 12.5–13 for immunodetection of biotinylated proteins. (E) Exogenous (left) and endogenous (right) Par3 is biotinylated by BL-Pk3 but not BL-Vangl2. Three bands that correspond to endogenous Par3 isoforms (bracket) are pulled down and detected by anti-Par3 antibodies, however only the top band corresponds to exogenous GFP-Par3 (arrowheads). Protein levels are shown by immunoblotting with anti-Myc and anti-FLAG antibodies in (A–C) and anti-biotin, anti-Par3, anti-FLAG and anti-GFP antibodies in (E).