The eukaryotic class 1 polypeptide chain release factor is a three-domain protein involved in the termination of translation, the final stage of poly-peptide biosynthesis. In attempts to understand the roles of the mid-dle domain of the eukaryotic class 1 polypeptide chain release factor in the transduction of the termination signal from the small to the large ribo-somal subunit and in peptidyl-tRNA hydrolysis, its high-resolution NMR structure has been obtained.