The structure of helix 89 of 23S rRNA is important for peptidyl transferase function of Escherichia coli ribosome

Helix 89 of the 23S rRNA connects ribosomal peptidyltransferase center and elongation factor binding site. Secondary structure of helix 89 determined by X-ray structural analysis involves less base pairs then could be drawn for the helix of the same primary structure. It can be that alternative secondary structure might be realized at some stage of translation. Here by means of site-directed mutagenesis we stabilized either the “X-ray” structure or the structure with largest number of paired nucleotides. Mutation UU2492-3C which aimed to provide maximal pairing of the helix 89 of the 23S rRNA was lethal. Mutant ribosomes were unable to catalyze peptide transfer independently either with aminoacyl-tRNA or puromycin.

► Helix 89 of the 23S rRNA connects ribosomal peptidyltransferase center and elongation factor binding site. ► Secondary structure of this helix could be suggested to maximize basepairing. ► We created mutations which should stabilize either the “native” or “maximal pairing” secondary structure. ► The mutation which stabilizes “maximal pairing” secondary structure is inviable. ► The reason for viability loss is inability to catalyze peptide transfer.