Fig. 9. Co-immunoprecipitation of Syt IX and tubulin from intact RBL cells. Immunoprecipitation was performed as described under Materials and Methods, using either the indicated immunoprecipitating antibody (IP Ab) followed by protein A Sepharose or incubated with protein A Sepharose without prior incubation with the primary antibody. Immune complexes were separated by SDS-PAGE and analyzed by Western blot using the indicated antibody (IB Ab).