FIG. 4.

Sucrose gradient analysis of N protein dimers in the presence or absence of NEM. PRRSV-infected cells were solubilized either in the absence (A) or presence (B) of 20 mM NEM, centrifuged at 14,000 rpm to remove insoluble materials, and then separated on a 10 to 40% linear sucrose gradient at 45,000 (model XL-90; Beckman) rpm for 20 h. Samples from designated fractions were run under nonreducing (−βME) (top) or reducing (+βME) (bottom) conditions and then transferred to nitrocellulose membranes. The membranes were probed with N-specific rabbit antibody. Sedimentation is from left to right. The arrows indicate monomers (N) and dimers (2N) of the N protein.