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Eukaryotic translation termination is mediated by two interacting release factors, eukaryotic class 1 release factor (eRF1) and eukaryotic class 3 release factor (eRF3), which act cooperatively to ensure efficient stop codon recognition and fast polypeptide release. eRF1 consisting of three well-defined functional domains recognizes all three mRNA stop codons located in the A site of the small ribosomal subunit and triggers hydrolysis of the ester bond of peptidyl-tRNA in the peptidyl transfer center of the large ribosomal subunit. Nevertheless, various aspects of molecular mechanism of translation termination in eukaryotes remain unclear. Elucidation of the structure and dynamics of eRF1 in solution is essential for understanding molecular mechanism of its function in translation termination. To approach this problem, here we report NMR backbone signal assignments of the human eRF1 (437 a.a., 50 kDa). [ABSTRACT FROM AUTHOR]

Abstract: Although some data link archaeal and eukaryotic translation, the overall mechanism of protein synthesis in archaea remains largely obscure. Both archaeal (aRF1) and eukaryotic (eRF1) single release factors recognize all three stop codons. The archaeal genus Methanosarcinaceae contains two aRF1 homologs, and also uses the UAG stop to encode the 22nd amino acid, pyrrolysine. Here we provide an analysis of the last stage of archaeal translation in pyrrolysine-utilizing species. We demonstrated that only one of two Methanosarcina barkeri aRF1 homologs possesses activity and recognizes all three stop codons. The second aRF1 homolog may have another unknown function. The mechanism of pyrrolysine incorporation in the Methanosarcinaceae is discussed. [Copyright &y& Elsevier]