FIG. 4.

Immunoblot showing that mutant B5R proteins are released from infected cells. RK₁₃ cells were infected with the indicated viruses at 10 PFU/cell and incubated in MEM with 2.5% FBS for 24 h. The supernatants of infected cells were clarified by low-speed centrifugation (2,000 rpm in a Beckman GPR benchtop centrifuge for 10 min) to pellet detached cells and cell debris and then high-speed centrifugation (14,000 rpm; SW28 rotor; Beckman ultracentrifuge; 80 min) to pellet virus particles (lanes V) from soluble protein (lanes S). An infected cell extract (C) was prepared as for Fig. 3. B5R proteins were resolved by electrophoresis and detected as described for Fig. 3. Molecular weight markers are shown in kilodaltons.