Hydrophobic interactions of Escherichia coli ribosomes

We have demonstrated the presence of hydrophobic sites on the surface of Escherichia coli ribosomes by means of hydrophobic chromatography on Octyl-Sepharose. Both 30-S and 50-S ribosomal subunits adsorb to Octyl-Sepharose at a low salt concentration, and can be eluted from it with a nonionic detergent without substantial changes in structure or activity. By testing a series of LiCl-derived ribosomal cores for their ability to adsorb to Octyl-Sepharose we have shown that the interaction of ribosomal particles with Octyl-Sepharose is dependent on the presence of certain ribosomal proteins; the core particles which lack these proteins do not bind to Octyl-Sepharose. The binding of a series of different ribosomal cores to nitrocellulose filters (Millipore) yielded the same pattern as was observed with Octyl-Sepharose, i.e. the more protein-depleted the particles, the less they were adsorbed. Thus, the adsorption of ribosomes to Millipore filters and to Octyl-Sepharose is presumably of the same hydrophobic nature.