Domain II of the eukaryotic class II release factor-like proteins
This model represents the domain similar to domain II of the eukaryotic class II release factor (eRF3). In eukaryotes, translation termination is mediated by two interacting release factors, eRF1 and eRF3, which act as class I and II factors, respectively. eRF1 functions as an omnipotent release factor, decoding all three stop codons and triggering the release of the nascent peptide catalyzed by the ribosome. eRF3 is a GTPase, which enhances termination efficiency by stimulating eRF1 activity in a GTP-dependent manner. Sequence comparison of class II release factors with elongation factors shows that eRF3 is more similar to eEF-1alpha whereas prokaryote RF3 is more similar to EF-G, implying that their precise function may differ. Only eukaryote RF3s are found in this group. Saccharomyces cerevisiae eRF3 (Sup35p) is a translation termination factor which is divided into three regions N, M and a C-terminal eEF1a-like region essential for translation termination. Sup35NM is a non-pathogenic prion-like protein with the property of aggregating into polymer-like fibrils. This group also contains proteins similar to S. cerevisiae Hbs1, a G protein known to be important for efficient growth and protein synthesis under conditions of limiting translation initiation and to associate with Dom34. It has been speculated that yeast Hbs1 and Dom34 proteins may function as part of a complex with a role in gene expression.
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