X-ray solution-scattering studies of active and inactive Escherichia coli ribosomal subunits.

That ribosomal subunits can exist in active and inactive functional states, and that subunits in the two states are interconvertible, has been known for some time (see Zamir et al., 1974). The magnitude of the conformational perturbation accompanying this functional transformation, however, was not known. In the present study 30 S and 50 S subunits in the two functional states have been compared by small-angle X-ray scattering. The results indicate that the structural differences between active and inactive subunits are small, at the limit of resolution of this technique. Model studies show that the data imply conformational differences at or below the limit of resolution of other physical methods now in use to examine the detailed structure of these particles.