Mapping the messenger RNA within the elongating ribosome

The method of proton-spin contrast-variation was applied for determining the position of the messenger RNA within the elongating ribosome. Using an artificial mRNA fragment the mass center of the mRNA sequence covered by the ribosome could be localized for the pre- and the post-translocational elongation states. The mass center moves about 12 +/- 5 Angstrom upon translocation. The radius of gyration was 12 +/- 3 Angstrom. The data give an independent contribution for refining a structural model including the RNA ligands of the elongating ribosome.