Translation termination factor aRF1 from the archaeon Methanococcus jannaschii is active with eukaryotic ribosomes

Class-1 translation termination factors (release factors (RFs)) from Eukary a (eRF1) and Archaea (aRF1) exhibit a high degree of amino acid sequence ho mology and share many common motifs. In contrast to eRF1, function(s) of aR F1 have not yet been studied in vitro. Here, rye describe for the first tim e the cloning and expression in Escherichia coli of the gene encoding the p eptide chain RF from the hyperthermophilic archaeon Methanococcus jannaschi i (MjaRF1). In an in vitro assay with mammalian ribosomes, MjaRF1, which wa s overproduced in E. coli, was active as a RF with all three termination co don-containing tetraplets, demonstrating the functional resemblance of aRF1 and cRF1, This observation confirms the earlier prediction that eRF1 and a RF1 form a common structural-functional eRF1/aRF1 protein family, originati ng from a common ancient ancestor. (C) 2000 Federation of European Biochemi cal Societies.