Revealing structure and folding requirements of 23S rRNA along the assembly pathway to catalytically active 50S subunits: SELEX of E.coli 23S rRNAs, functional in the absence of posttranscriptional modifications

Erwin Schrödinger Position J 1920 In vitro selection of E.coli 23S rRNA Katharina SEMRAD 26.6.2000 The 23S rRNA of large ribosomal subunit is a good candidate for providing functional groups directly involved in the catalysis of peptide bond formation. It was shown that in vitro assembled 50S subunits of E.coli (derived from in vivo generated RNA and protein components) are able to catalyse peptide bond formation. However, if the E.coli 23S rRNA is transcribed in vitro and reconstituted with total proteins from the 50S subunit (TP50), no peptidyl transferase (PT) activity is observed. An 80 nucleotide fragment was identified where in vivo derived post-transcriptional modifications are essential to obtain PT competent 50S subuints. These modifications are believed to be involved in folding, but not in catalysis. A SELEX experiment starting from a mutagenized 23S rRNA pool will isolate 23S rRNA mutants that can competently assemble into functional 50S subunits in the absence of post-transcriptional modifications.