Fig. 1. PSD-95 forms non-covalent multimers. COS cells were transfected with plasmids encoding GFP- and FLAG-tagged PSD-95 proteins as indicated. Cells were lysed with either 1% Triton X-100 or 0.1% SDS and proteins were immunoprecipitated with an antibody to GFP. Western blotting reveals that PSD-95/FLAG co-immunoprecipitated in cells lysed with Triton X-100 but not in SDS-treated lysates.