The function of METTL18 (methyltransferase 18, RPL3 N3(tau)-histidine, ENSG00000171806) is as follows. Protein-L-histidine N-tele-methyltransferase that specifically monomethylates RPL3, thereby regulating translation elongation (PubMed:23349634, PubMed:33693809, PubMed:35674491). Histidine methylation of RPL3 regulates translation elongation by slowing ribosome traversal on tyrosine codons: slower elongation provides enough time for proper folding of synthesized proteins and prevents cellular aggregation of tyrosine-rich proteins (PubMed:35674491). {ECO:0000269|PubMed:23349634, ECO:0000269|PubMed:33693809, ECO:0000269|PubMed:35674491}.