Physico-chemical and Reassociation Properties of E. coli Ribosomal Subunits

Publisher Website
Google Scholar
Abstract
Large amounts of 30, 50, and 70S ribosomes from Escherichia coli strain Q13 have been fractionated by sucrose density gradient sedimentation with a fixed angle rotor. The purity of each fractionated sample was satisfactory. The molecular weights of 30 and 50S subunits were measured by means of light scattering and values of 77.5 × 104 and 148 × 104 were obtained, respectively. The dimensions of 70S ribosomes and those of the subunits were determined from the values of intrinsic viscosity, radius of gyration, and partial specific volume. Measurements of the volume obtained by the former two methods gave values about 4 times larger than the volume calculated from partial specific volume and molecular weight. This suggests that the ribosomes are hydrated with a large amount of water and that they are swollen in solution. Experiments involving reassociation of the subunits revealed that fractionated subunits lose their ability to form 70S particles. A small RNA component obtained from 70S ribosomes on their dissociation to subunits played an important role in the reassociation of the subunits to 70S ribosomes. The component appeared to be a peptidyl (or aminoacyl)-tRNA. 30S subunit polymerized with itself to form dimer and trimer under some experimental conditions. However, there was no evidence that 50S subunit forms a dimer.

This publication has 0 references indexed in Scilit: