Mitochondrial translation termination

Mitochondrial translation termination Translation is terminated for 11 of the 13 mitochondrially encoded proteins when MTRF1L (MTRF1a) recognizes a UAA or UAG termination codon in the mRNA at the A site of the ribosome (Soleimanpour-Lichaei et al. 2007, reviewed in Richter et al. 2010, Chrzanowska-Lightowlers et al. 2011. Christian and Spremulli 2012). Translation of the MT-CO1 and MT-ND6 proteins is terminated at an AGG codon and an AGA codon, respectively. These two noncanonical stop codons are recognized by MTRF1. GTP is hydrolyzed, and the aminoacyl bond between the translated polypeptide and the final tRNA at the P site is hydrolyzed by the 39S ribosomal subunit, releasing the translated polypeptide. MRRF (RRF) and GFM2:GTP (EF-G2mt:GTP) then act to release the remaining tRNA and mRNA from the ribosome and dissociate the 55S ribosome into 28S and 39S subunits.