FIG. 3.

Detergent resistance of membrane-associated M1 when coexpressed with influenza virus HA and NA. For coexpression studies, HeLa cells (5 × 10⁶) were infected with RVV expressing M1 alone or M1 in combination with HA or NA or with both HA and NA proteins as stated in Materials and Methods. At 4 hpi, cells were labeled with 400 μCi of ³⁵S Easy Tag for 30 min and chased for 90 min. Cells were fractionated, and pure membrane fractions of the 4K supernatant were isolated with a floatation gradient as stated in Materials and Methods. Aliquots of membrane fractions were either untreated (−) or treated (+) with TX-100 (0.05%) and analyzed with a second floatation gradient. Fractions were collected, immunoprecipitated with anti-WSN antibodies, and analyzed by SDS-PAGE. (A) Expression of influenza virus M1 alone. (B) Coexpression of influenza virus M1 with influenza virus HA protein. (C) Coexpression of influenza virus M1 with NA protein. (D) Coexpression of M1 with both influenza virus HA and NA. Left-hand panels are without TX-100 treatment, and right-hand panels are after TX-100 treatment.