POSSIBLE INVOLVEMENT OF ESCHERICHIA-COLI 23S RIBOSOMAL-RNA IN PEPTIDE-BOND FORMATION

Experimental results are presented suggesting that 23S rRNA is directl y involved in the peptide bond formation usually performed on the ribo some. Although several reports have indicated that the eubacterial pep tidyltransferase reaction does not necessarily require all the ribosom al proteins, the reconstitution of peptidyltransferase activity by a n aked 23S rRNA without the help of any of the ribosomal proteins has no t been reported previously, It is demonstrated that an E. coli23S rRNA transcript synthesized by T7 RNA polymerase in vitro was able to prom ote peptide bond formation in the presence of 0.5% SDS. The reaction w as inhibited by the peptidyltransferase-specific antibiotics chloramph enicol and carbomycin, and by digestion with RNases A and T1. Site-dir ected mutageneses at two highly conserved regions close to the peptidy ltransferase center ring, G2252 to U2252 and C2507G2581 to U2507A2581, also suppressed peptide bond formation. These findings strongly sugge st that 23S rRNA is the peptidyltransferase itself.