Direct shape determination of ribosomal proteins in solution and within the ribosome by means of neutron scattering.

Following the 'strategy of the glassy ribosome' single protonated ribosomal proteins (r-proteins) were reconstituted into deuterated 50S subunits of Escherichia coli. The deuteration of both rRNA and r-proteins were individually adjusted to such a degree that the ribosomal matrix appeared nearly homogeneous with respect to coherent neutron scattering and had a scattering density equivalent to a D2O solution of about 90%. Neutron scattering of ribosomal subunits was recorded in reconstitution buffer containing three different concentrations of D2O around 90% D2O (contrast variation). The signal-to-noise ratio achieved allowed us to make a direct determination of the radii of gyration of r-proteins within the 50S subunit and thus provides the first information relating to the shape of these proteins in situ. We present the radii of gyration of 11 r-proteins incorporated into 50S subunits and of 9 isolated r-proteins in solution. In addition, the data concerning the overall dimensions of the r-proteins we report on indicate that conformational changes of at least two individual r-proteins occur during the assembly process of the ribosome.