FIG. 2.

Dissociation of VLPs by salt. (A) VLP-associated RT activity in low-ionic-strength buffer and in a buffer containing 0.5 M NaCl. Wild-type VLPs were prepared as described by Eichinger and Boeke (8). One half of the VLP preparation was fractionated on a step gradient containing a low-ionic-strength buffer. NaCl was added to the other half to a final concentration of 0.5 M. The salt-treated VLPs were fractionated on a sucrose step gradient containing the same concentration of NaCl. RT activity was assayed on fractions of the density gradient. (B and C) Immunoblotting of gradient fractions using anti-RT (B) and anti-Gag (C) antibodies.