Fig. 2. The N-terminal 13 amino acids of PSD-95 can mediate homomultimerization. COS cells were transfected with plasmids as indicated. Cell lysates were immunoprecipitated with antibodies to GFP or to the PDZ domains of PSD-95 as indicated and western blotting was used to monitor co-immunoprecipitation. (A) FLAG-tagged full-length PSD-95 and amino acids 1-13 of PSD-95 fused to GFP efficiently co-immunoprecipitated. (B) COS cells were co-transfected with constructs encoding PSD-95-GFP and amino acids 1-13 of PSD-95 fused to GFP. Co-immunoprecipitation of these constructs is disrupted when cells are lysed in buffer containing 0.1% SDS. (C) Chimeras of GFP and maltose binding protein (MBP), each containing the first 13 amino acids of PSD-95, efficiently co-immunoprecipitate.