Mapping of Escherichia coli ribosomal components involved in peptidyl transferase activity.

The method of affinity labeling has been used to identify protein components of 50S ribosomal subunits involved in peptidyl transferase activity. E. coli 50S ribosomal subunits were mapped by reaction with the N-bromoacetyl analog of chloramphenicol, an antibiotic known to interact specifically with the active center of the enzyme. The synthetic analog competes with chloramphenicol in binding to 50S ribosomal subunits and inhibits peptidyl transferase activity. It attaches covalently to the ribosome under appropriate conditions and causes an irreversible loss in peptidyl transferase activity. The reagent specifically alkylates cysteine residues of proteins L2 and L27.