FIG. 6.

Amino one-third of BPP is required for its capsid interaction. Lysates of nuclei from SCMV-infected cells were combined with ³⁵S-sBPP or with [³⁵S]methionine-labeled truncation mutants of sBPP and assayed by centrifugation, SDS-PAGE, and phosphorimaging. Shown here are the relevant portions of the resulting phosphorimages. The proteins tested were SCMV BPP (amino acids 1 to 762) (A); the carboxyl truncations δC321 (amino acids 1 to 441) (B), δC487 (amino acids 1 to 275) (C), and δC568 (amino acids 1 to 194) (D); the amino truncations δN275 (amino acids 276 to 762) (E), δN193 (amino acids 194 to 762) (F), and δN99 (amino acids 100 to 762) (G); and a mutant lacking both amino and carboxyl sequences, δN193/δC487 (amino acids 194 to 275) (H). The data are from two separate experiments, the first shown in panels A to D and the second shown in panels E to H. Because of its small size, the gradient samples for the 9.5-kDa double-deletion mutant, 194 to 275, were subjected to SDS-PAGE in two parallel Tricine 10 to 20% gradient gels (no. EC66255; Novex, San Diego, Calif.). The fractions containing B-capsids were identified by protein staining and are indicated by the letter B. The asterisks denote the full-length test protein. The amino acid sequence represented by the test protein is indicated in the lower right-hand corner of each panel. Samples of the starting reticulocyte preparations are shown in the leftmost lane of each panel. The mutant proteins are depicted schematically in Fig. 7.