Engineered 23S rRNAs and methods of use thereof for translation of proteins incorporating non-standard amino acids are provided. Typically, the 23S rRNA includes one or more mutations at positions 2496-2507 relative to E. coli wildtype 23S rRNA, wherein a ribosome composed of the 23S rRNA can catalyze the covalent transfer of a non-standard amino acid from an aminoacyl-RNA onto a nascent peptide chain. For example, the 23S rRNA can include the sequence UGACUU at positions 2502-2507 relative to E. coli wildtype 23S rRNA, and optionally the sequence AGCGUGA from positions 2057-2063 relative to E. coli wildtype 23S rRNA. The 23S rRNA can include additional or alternative deletions, substitutions, insertions, or combination thereof. The compositions and methods can be used to make polypeptides and sequence defined polymers.