Reconstruction of peptidyltransferase activity on 50S and 70S ribosomal particles by peptide fragments of protein L16.

Ribosomal protein L16 was digested with Staphylococcus aureus protease V8 and the resulting peptides were separated by reversed-phase high-performance liquid chromatography. One of the fragments, identified by sequence analysis as the N-terminal peptide of L16, was shown to exhibit partial peptide-bond-formation and transesterification activities of peptidyltransferase upon reconstitution with L16-depleted 50S core particles. However, several proteins enhanced these activities. L15 increased both reactions when added to the reconstitution mixture, suggesting a limited capacity of the L16 peptide to incorporate into 50S core particles. In contrast, the interaction of L11 with the N-terminal peptide stimulated the transesterification reaction but not the peptide-bond-forming activity of ribosomes, indicating a different topological domain for these reactions. Also, EF-P, a soluble protein which reconstructs the peptide-bond formation and transesterification reactions on 70S ribosomes, stimulated both peptidyltransferase activities exhibited by the L16 N-terminal peptide.