BBS4 has an IFT-like distribution within the cell. (A) Dish phototaxis assay of wild type, bbs4-1, and BBS4HA21 rescued by BBS4-3xHA. (B) Western blot of flagella from the strains shown in C probed with monoclonal anti-HA. (C) BBS4HA21 cells labeled by anti–α-tubulin and anti-HA. BBS4-3xHA is located near the basal bodies (arrowhead) and in dots along both flagella. (D) Western blot of BBS4HA21 to compare the amounts of various proteins in cell bodies (CB) versus isolated flagella (FLA). 1× indicates that approximately two flagella were loaded per cell body, etc. The blot was probed for BBS4-HA, IC2, and IFT57 and -81. BBS4-3xHA is about eight times more abundant in cell bodies than in flagella. (E) Western blot analyzing equivalent amounts of whole flagella, axonemes (AXO), and NP-40–soluble membrane-plus-matrix (M&M) of flagella from BBS4HA21 and wild-type cells. Antibodies were as indicated; those to IC2 and various IFT particle proteins were used as controls. (F) Western blot comparing equivalent amounts of wild-type flagella, axonemes, AP, and DP resulting from Triton X-114 phase partitioning. The blot was probed with the antibodies indicated. (B and D–F) The positions of standard proteins and their molecular masses in kilodaltons are indicated. Bar, 5 µm.