RIBOSOMES AND RIBOSOMAL-RNA AS CHAPERONES FOR FOLDING OF PROTEINS

Background: Provocative recent reports indicate that the large subunit s of either prokaryotic or eukaryotic ribosomes have the capacity to p romote refolding of denatured enzymes. Results: Salt-washed Escherichi a coli ribosomes are shown to promote refolding of denatured rhodanese . The ability of the ribosomes to carry out renaturation is a property of the 50S ribosomal subunit, specifically the 23S rRNA. Refolding an d release of enzymatically active rhodanese leaves the ribosomes in an inactive state or conformation for subsequent rounds of refolding. In active ribosomes can be activated by elongation factor G (EF-G) plus G TP or by cleavage of their 23S rRNA by alpha-sarcin. Activation by eit her mechanism is strongly inhibited by the EF-G.GDP.fusidic acid compl ex. Conclusions: Large subunits of E. coli ribosomes, specifically 23S rRNA, have the capacity to mediate refolding of denatured rhodanese. Refolding activity is related to the state or conformation of ribosome s that is promoted by EF-G. Activation by either mechanism is strongly inhibited by the EF-G.GDP.fusidic acid complex.