Asymmetry in the 50S ribosomal subunit of Escherichia coli.

A substantial separation of the centers of mass of the protein and RNA portions of the 50S ribosomal subunit has been achieved using neutron scattering. This separation reveals that the subunit has a protein-rich side, a finding which is inconsistent with many models proposed for the structure. By analyzing the variation of the radius of gyration of the subunit under conditions in which the contributions of the protein and RNA were separately enhanced by deuteration and comparing these radii to the undeuterated subunit radius, we have obtained the following values. The radius of gyration of the whole particle is 78.0 +/- 0.95 A, that of the RNA moiety is 72.5 +/- 1.5 A, and that of the protein is 73.4 +/- 2.0 A. These data give a separation of the centers of mass of the RNA and protein distributions of 57.7 +/- 10 A.