RNA-binding component of the large ribosomal subunit. The ribosome is a large ribonucleoprotein complex responsible for the synthesis of proteins in the cell. {ECO:0000269|PubMed:23636399, ECO:0000269|PubMed:32669547, ECO:0000269|PubMed:8764829}. This is the function of RPL39 (ribosomal protein L39, ENSG00000198918).