This protein binds directly to 23S ribosomal RNA and is located at the A site of the peptidyltransferase center. It contacts the A and P site tRNAs (PubMed:8524654). It has an essential role in subunit assembly, which is not well understood (PubMed:3298242). Part of the 50S ribosomal subunit (PubMed:786730, PubMed:10094780, PubMed:12809609, PubMed:16272117, PubMed:25310980, PubMed:24844575, PubMed:27934701, PubMed:27906160, PubMed:27906161). Cross-links to the A and P site tRNAs (PubMed:8524654). Is hydroxylated on Arg-81 by RoxA. The modification is nearly suppressed when E.coli is grown in anoxia. Belongs to the universal ribosomal protein uL16 family.