FIGURE 1.

Characterization of spliceosomal A complexes purified via tobramycin affinity selection followed by immunoaffinity selection and gradient centrifugation. Complexes were separated on a 10%–30% glycerol gradient. RNA was recovered from each gradient fraction (as indicated above), analyzed by denaturing PAGE, and visualized by silver staining (upper panel) or by autoradiography (lower panel). The identity of the various RNAs is indicated on the right. Contaminating high molecular weight RNAs are indicated by an asterisk. “PRE” indicates the pre-mRNA. 30S and 50S correspond to migration positions of E. coli ribosomal subunits in parallel gradients.