Solution scattering from 50S ribosomal subunit resolves inconsistency between electron microscopic models.

Models of the 50S ribosomal subunit from electron microscopy on isolated particles and on ordered sheets display significantly different features. A model of the shape of the native Escherichia coli 50S subunit in solution and of its RNA-rich core at 4-nm resolution has been produced by using methods for joint interpretation of x-ray and neutron small-angle scattering data obtained by contrast variation. The good agreement between the shape of the entire 50S subunit and the electron microscopic models of isolated particles and between the RNA-rich core and the model obtained from ordered sheets leads to the conclusion that the latter, which is based on the subjective contouring of density maps, is heavily biased toward the RNA.