Disassembly of yeast 80S ribosomes into subunits is a concerted action of ribosome-assisted folding of denatured protein

It has been shown by several groups that ribosome can assist folding of denatured protein in vitro and the process is conserved across the species. Domain V of large ribosomal rRNA which occupies the inter subunit side of the large subunit was identified as the key player responsible for chaperoning the folding process. Thus, it is conceivable that denatured protein needs to access the intersubunit space of the ribosome in order to get folded. In this study, we have investigated the mechanism of release of the protein from the eukaryotic ribosome following reactivation. We have observed significant splitting of yeast 80S ribosome when incubated with the denatured BCAII protein. Energy-free disassembly mechanism functions in low Mg+2 ion concentration for prokaryotic ribosomes. Eukaryotic ribosomes do not show significant splitting even at low Mg+2 ion concentration. In this respect, denatured protein-induced disassembly of eukaryotic ribosome without the involvement of any external energy source is intriguing. For prokaryotic ribosomes, it was reported that the denatured protein induces ribosome splitting into subunits in order to access domain V-rRNA. In contrast, our results suggest an alternative mechanism for eukaryotic ribosomal rRNA-mediated protein folding and subsequent separation of the subunits by which release of the activated-protein occurs. (C) 2015 Elsevier Inc. All rights reserved.