Fig. 9. Western blot analysis of various truncated VM32E-MYC chimeric proteins. (A) Staged egg chambers treated as described in Materials and Methods. The VM32E-MYC and 1 constructs show the same protein extraction pattern as the wild-type VM32E protein. The 2 protein shows a strong signal in the S phase of stage 10B, indicating that a significant proportion of its molecules are not yet integrated into the membrane. A remarkable feature of 3 protein is the high amount extracted from the pellet of stage 14. (B) Stage 14 egg chambers processed in presence of 2% SDS. The 2 protein is fully solubilized by SDS, whereas the 3 protein appears cross-linked by disulfide bridges. (C) Western blot analysis of 2 and 3 proteins in laid eggs. As with the wild-type VM32E protein, the 3 protein appears tightly integrated in the vitelline membrane. The released amount of 2 protein is the same from whole (+Ch.) or dechorionated (-Ch.) eggs, suggesting tight cross-linking only in the chorion layer. (D) Structure of the three VM32E deletions analyzed here.