Contrast variation study of specifically deuterated Escherichia coli ribosomal subunits.

A neutron small-angle scattering analysis has been done on partially deuterated 30S and 50S subunits of Escherichia coli ribosomes by the contrast variation method. The results indicate that the central regions of both particles are RNA-rich whereas their exteriors are protein-rich. The segregation of RNA and protein is much greater in the 50S subunit than in the 30S; the 30S subunit approaches a homogeneous mixture of RNA and protein. In both structures the most probable separation between the centers of mass of their protein and RNA distributions is small, although substantial variation of this parameter is possible within experimental error.