Electron microscopy study of Qβ replicase

Purified preparations of Qβ replicase have been studied by electron microscopy using a negative staining technique, and a three-dimensional model of the enzyme molecule has been constructed. The molecule of this four-subunit protein appears to be a compact structure having a size of 100 ± 10 A; it is subdivided into two unequal bipartite subparticles. The conclusion has been made that all the constituent subunits, including the ribosomal protein S1, acquire a globular conformation when associated in the replicase complex.