FIG. 5.

Competition for cross-linking of the 65-kDa protein. The ³²P-labeled wild-type apo-B RNA was incubated with proteins eluted from the wild-type RNA affinity column in the absence of competitor (none) or in the presence of a 2.5-, 5-, 7.5-, 10-, or 50-fold molar excess of unlabeled wild-type apo-B RNA; a 500- or 1,000-fold molar excess of the triple-mutant RNA; or a 500-fold molar excess of the antisense apo-B RNA. UV cross-linking and SDS–8% PAGE were performed as described in the legend to Fig. 3. The position of the 65-kDa protein is indicated by an arrow. Molecular size markers (in kilodaltons) are indicated on the right.