FIG. 7.
Higher-order structure of the covalently linked GP2b/GP4 and GP2b/GP3/GP4 complexes. Concentrated [35S]cysteine-labeled EAV particles were dissolved in MNT-0.4% Triton (pH 5.8) and loaded onto a 5 to 20% (wt/wt) sucrose density gradient. After centrifugation for 52 h at 38,000 rpm and 4°C in an SW41 rotor, fractions were collected and subjected to immunoprecipitations with αGP2b. The immunoprecipitates were analyzed in SDS-15% PAA gels under nonreducing conditions. Fraction numbers are indicated above the autoradiograph. In lane P, the material from the bottom of the gradient was analyzed. As a reference, the immune complexes obtained after incubation of an aliquot of solubilized EAV particles with αGP2b was run in parallel (lane V). Arrows indicate the positions of the marker proteins ovalbumin (45 kDa) and bovine albumin (66 kDa) in another 5 to 20% (wt/wt) sucrose density gradient of the same spin. The numbers on the left are the molecular masses, in kilodaltons, of marker proteins analyzed in the same gel.