A comparative study on the hydrodynamic shape, conformation, and stability of E. coli ribosomal subunits in reconstitution buffer

Abstract

We have compared the hydrodynamic shape, conformation, and stabilities of active, unwashed ribosomal subunits, as well as their susceptibilities to changes in temperature and ionic strength. Both intrinsic viscosity and sedimentation velocity measurements indicate that the 30 S subunit has a more asymmetric hydrodynamic shape. The intrinsic viscosity of this subunit in reconstitution buffer has been found to be significantly larger than the value reported previously. While the RNA conformation in both subunits may be very similar as suggested by the near uv CD spectra, the average conformation of the protein in the two subunits is drastically different. The 30 S subunit has a lower T m. The 50 S subunit is rather stable toward changes of ionic strength, whereas the 30 S subunit is quite susceptible to changes in ionic strength.