3 TRANSFER-RNA BINDING-SITES IN RABBIT LIVER RIBOSOMES AND ROLE OF THE INTRINSIC ATPASE IN 80S RIBOSOMES FROM HIGHER EUKARYOTES

Three tRNA binding sites have been found in organisms of all domains ( former kingdoms) with only one exception: Four binding sites have been reported for cytoplasmic 80S ribosomes from rabbit liver. Therefore, the issue was reconsidered, and the data revealed that rabbit liver ri bosomes contain three tRNA binding sites, underlining the universal ch aracter of this ribosomal feature. Furthermore, a first analysis of th e role of the ribosome intrinsic ATPase was performed. This ATPase is found in ribosomes bf higher eukarya but not in lower eukarya such as yeast or ribosomes of the domains archea and bacteria. The results sug gest that the intrinsic ATPase fulfills the same function as the essen tial third elongation factor EF-3, an ATPase in higher fungi (yeast et c.), that facilitates the release of the deacylated tRNA from the E si te.