Structural changes of ribosome by the action of ethylene glycol

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Abstract
The denaturation of [Escherichia coli] ribosome and RNA by ethylene glycol (EG) was studied in an attempt to further understand the conformation and stability of the ribosome. At high concentrations of EG, the ribosome, its subunits and 16S RNA undergo drastic structural changes as shown by circular dichroism, UV absorption spectroscopy and sedimentation velocity. Two separate conformational transitions were observed for the 30S subunit; 1 from 30-50% EG and another from 60-90% EG. This observation suggests the presence of 2 domains in the 30S subunit which differ in their stability. The 50S subunit undergoes a single sharp transition at 60-90% EG, consistent with the notion of a highly cooperative conformation. Association of the subunits stabilizes part of the 30S subunit since the transition curve for the 70S ribosome does not exhibit significant change at the low EG concentration region as seen for the 30S subunit. Removal of proteins from the 30S subunit broadens the transition curve to lower EG concentrations and suggests the role of proteins in stabilizing the conformation of the 16S RNA.