FIG. 4.

Detergent resistance of membrane-associated M1 when coexpressed with chimeric constructs of influenza virus HA and Sendai virus F proteins. (A) Schematic presentation of chimeric constructs between Sendai virus F and influenza virus HA. aa, amino acids; Cyt., cytoplasmic. (B to F) Detergent-resistant membrane fractions of M1 in the presence of heterologous or chimeric proteins. HeLa cells (5 × 10⁶) were infected with RVV expressing M1 alone (B) or M1 with Sendai virus F (C), M1 with FHH (D), M1 with HHF (E), or M1 with FFH (F) as described in Materials and Methods. At 4 hpi, cells were pulse-labeled with 400 μCi of ³⁵S Easy Tag for 30 min and chased for 90 min. Pure membrane fractions were isolated from 4K supernatants with floatation gradients, treated without (−) or with (+) TX-100 (0.05%), and analyzed again with floatation gradients. Fractions were collected, immunoprecipitated, and analyzed by SDS-PAGE. (G) Expression of F and chimeric proteins. HeLa cells (5 × 10⁶) were infected with RVV expressing F, FHH, HHF, and FFH. At 4 hpi, cells were pulse-labeled for 30 min and chased for 90 min. The whole-cell extract was immunoprecipitated and analyzed by SDS-PAGE. Note that similar levels of F and chimeras were expressed. Lanes 1, marker; lanes 2, FHH; lanes 3, FFH; lanes 4, HHF; lanes 5, F.