Fig. 9. Multimerization of BEGAIN via the N-terminal region. A, Multimerization of GFP-BEGAIN-2. Extracts of HeLa cells expressing GFP-BEGAIN-2 or -4 were analyzed on glycerol density gradient, and fractions were immunoblotted with anti-GFP antibody. Numbers at the bottom indicate fraction numbers. The first lanes contain original extracts. Top arrows indicate positions of peaks of marker proteins composed of thyroglobulin (21.7 S, 670 K), bovine γ-globulin (7.8 S, 158 K), chicken ovalbumin (3.7 S, 44 K), and equine myoglobin (2.0 S, 17.5 K). Top panel, GFP-BEGAIN-2; bottom panel, GFP-BEGAIN-4. GFP-BEGAIN-2 has two peaks. Asterisk indicates the first peak of GFP-BEGAIN-2 that corresponds to dimers in the glycerol density gradient, and the protein migrates as monomers in SDS-PAGE.Double asterisk indicates the second peak as tetramers, and the protein migrates as dimers in SDS-PAGE. GFP-BEGAIN-4 is recovered as monomers both in the glycerol density gradient and in SDS-PAGE (#). B, Coimmunoprecipitation of the N-terminal region of BEGAIN with the full length of BEGAIN. Extracts of COS cells expressing Myc-BEGAIN-2 with or without Myc-BEGAIN-1 were immunoprecipitated with anti-BEGAIN-C antibody that bound only Myc-BEGAIN-1. Immunoprecipitates were immunoblotted with anti-Myc antibody to see whether Myc-BEGAIN-2 was coimmunoprecipitated.Open arrowheads indicate Myc-BEGAIN-1 and -2.Lanes 1 and 4, Original extracts;lanes 2 and 5, precipitates with preimmune serum; lanes 3 and 6, precipitates with anti-BEGAIN-C antibody. Lanes 1,2, and 3, Without Myc-BEGAIN-1;lanes 4, 5, and 6, with Myc-BEGAIN-1.